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University of the Philippines - DilimanMath DepartmentMath 53 Lecture Slides

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Review of Functions

Mathematics 53

Institute of Mathematics - UP Diliman

8 November 2012

Math 53 (Part 1) Review of Functions 8 November 2012 1 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 2 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 3 / 69

Functions

DefinitionLet X and Y be nonempty sets. A function f from X to Y, denoted f : X → Y, isa rule that assigns to each element of X a unique element of Y.

X: domain of f , denoted dom fY: codomain of fThe set of all elements of Y that are assigned to some element of X is therange of f , denoted ran f

Math 53 (Part 1) Review of Functions 8 November 2012 4 / 69

Functions

DefinitionLet X and Y be nonempty sets. A function f from X to Y, denoted f : X → Y, isa rule that assigns to each element of X a unique element of Y.

X: domain of f , denoted dom f

Y: codomain of fThe set of all elements of Y that are assigned to some element of X is therange of f , denoted ran f

Math 53 (Part 1) Review of Functions 8 November 2012 4 / 69

Functions

DefinitionLet X and Y be nonempty sets. A function f from X to Y, denoted f : X → Y, isa rule that assigns to each element of X a unique element of Y.

X: domain of f , denoted dom fY: codomain of f

The set of all elements of Y that are assigned to some element of X is therange of f , denoted ran f

Math 53 (Part 1) Review of Functions 8 November 2012 4 / 69

Functions

DefinitionLet X and Y be nonempty sets. A function f from X to Y, denoted f : X → Y, isa rule that assigns to each element of X a unique element of Y.

X: domain of f , denoted dom fY: codomain of fThe set of all elements of Y that are assigned to some element of X is therange of f , denoted ran f

Math 53 (Part 1) Review of Functions 8 November 2012 4 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}codomain: Y = {0, 1, 2, 3, 4}range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}codomain: Y = {0, 1, 2, 3, 4}range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f

= {−2,−1, 0, 1, 2}codomain: Y = {0, 1, 2, 3, 4}range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}

codomain: Y = {0, 1, 2, 3, 4}range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}codomain: Y

= {0, 1, 2, 3, 4}range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}codomain: Y = {0, 1, 2, 3, 4}

range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}codomain: Y = {0, 1, 2, 3, 4}range: ran f

= {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

−2 7−→ 4−1 7−→ 10 7−→ 01 7−→ 12 7−→ 4

domain: dom f = {−2,−1, 0, 1, 2}codomain: Y = {0, 1, 2, 3, 4}range: ran f = {0, 1, 4}

Math 53 (Part 1) Review of Functions 8 November 2012 5 / 69

Functions

If x ∈ X, the symbol f (x) denotes the element y ∈ Y that is assigned to x.

A function may be written as y = f (x)x: independent variable

y: dependent variable

Alternatively, a function f is a set of ordered pairs (x, y), where

(x, y) ∈ f if and only if y = f (x)

Math 53 (Part 1) Review of Functions 8 November 2012 6 / 69

Functions

If x ∈ X, the symbol f (x) denotes the element y ∈ Y that is assigned to x.

A function may be written as y = f (x)x: independent variable

y: dependent variable

Alternatively, a function f is a set of ordered pairs (x, y), where

(x, y) ∈ f if and only if y = f (x)

Math 53 (Part 1) Review of Functions 8 November 2012 6 / 69

Functions

If x ∈ X, the symbol f (x) denotes the element y ∈ Y that is assigned to x.

A function may be written as y = f (x)x: independent variable

y: dependent variable

Alternatively, a function f is a set of ordered pairs (x, y), where

(x, y) ∈ f if and only if y = f (x)

Math 53 (Part 1) Review of Functions 8 November 2012 6 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

The function f may be written as:

f (x) = x2 or y = x2

f = {(−2, 4), (−1, 1), (0, 0), (1, 1), (2, 4)}

Math 53 (Part 1) Review of Functions 8 November 2012 7 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

The function f may be written as:

f (x) = x2 or y = x2

f = {(−2, 4), (−1, 1), (0, 0), (1, 1), (2, 4)}

Math 53 (Part 1) Review of Functions 8 November 2012 7 / 69

Functions

ExampleConsider f : X → Y defined by the rule

x 7−→ x2

where X = {−2,−1, 0, 1, 2} and Y = {0, 1, 2, 3, 4}.

The function f may be written as:

f (x) = x2 or y = x2

f = {(−2, 4), (−1, 1), (0, 0), (1, 1), (2, 4)}

Math 53 (Part 1) Review of Functions 8 November 2012 7 / 69

Real-valued functions of a single variable

Real-valued functions of a single variable:

Codomain: R

Math 53 deals with functions whose domain and range are subsets of R.

If the domain is not explicitly specified:

Domain: dom f = {x ∈ R | f (x) is a real number}

Math 53 (Part 1) Review of Functions 8 November 2012 8 / 69

Real-valued functions of a single variable

Real-valued functions of a single variable:

Codomain: R

Math 53 deals with functions whose domain and range are subsets of R.

If the domain is not explicitly specified:

Domain: dom f = {x ∈ R | f (x) is a real number}

Math 53 (Part 1) Review of Functions 8 November 2012 8 / 69

Real-valued functions of a single variable

Example

1 f (x) = x2

dom f = R

2 f (x) =x2 − 2x− 3

x + 1

dom f = R \ {−1}

Math 53 (Part 1) Review of Functions 8 November 2012 9 / 69

Real-valued functions of a single variable

Example

1 f (x) = x2

dom f = R

2 f (x) =x2 − 2x− 3

x + 1

dom f = R \ {−1}

Math 53 (Part 1) Review of Functions 8 November 2012 9 / 69

Real-valued functions of a single variable

Example

1 f (x) = x2

dom f = R

2 f (x) =x2 − 2x− 3

x + 1dom f = R \ {−1}

Math 53 (Part 1) Review of Functions 8 November 2012 9 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0(x− 3)(x + 1) = 0

x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0(x− 3)(x + 1) = 0

x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0(x− 3)(x + 1) = 0

x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0

(x− 3)(x + 1) = 0x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0(x− 3)(x + 1) = 0

x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0(x− 3)(x + 1) = 0

x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Zeroes of a function

DefinitionA zero of a function f is a value of x for which f (x) = 0.

Example

Find the zero(es) of f (x) =x2 − 2x− 3

x + 1.

x2 − 2x− 3x + 1

= 0

x2 − 2x− 3 = 0(x− 3)(x + 1) = 0

x = 3 or x = −1

The only zero of f is x = 3.

Math 53 (Part 1) Review of Functions 8 November 2012 10 / 69

Graphs of Functions

DefinitionThe graph of a function f is the set of all points (x, y) in the plane R2 for which(x, y) ∈ f .

The graph of a function is the geometric representation on the Cartesian plane ofall points (x, y) that satisfy y = f (x).

Math 53 (Part 1) Review of Functions 8 November 2012 11 / 69

Graphs of Functions

DefinitionThe graph of a function f is the set of all points (x, y) in the plane R2 for which(x, y) ∈ f .

The graph of a function is the geometric representation on the Cartesian plane ofall points (x, y) that satisfy y = f (x).

Math 53 (Part 1) Review of Functions 8 November 2012 11 / 69

Graphs of Functions

Example

The graph of f (x) = x2:

−2 −1 1 2

1

2

3

4

0

The points on the graph of f are the points (x, y) that satisfy the equation y = x2.

Math 53 (Part 1) Review of Functions 8 November 2012 12 / 69

Graphs of Functions

Example

The graph of f (x) =x2 − 2x− 3

x + 1:

f (x) =x2 − 2x− 3

x + 1=

(x− 3)(x + 1)(x + 1)

= x− 3 if x 6= 1

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 13 / 69

Graphs of Functions

Example

The graph of f (x) =x2 − 2x− 3

x + 1:

f (x) =x2 − 2x− 3

x + 1

=(x− 3)(x + 1)

(x + 1)= x− 3 if x 6= 1

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 13 / 69

Graphs of Functions

Example

The graph of f (x) =x2 − 2x− 3

x + 1:

f (x) =x2 − 2x− 3

x + 1=

(x− 3)(x + 1)(x + 1)

= x− 3 if x 6= 1

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 13 / 69

Graphs of Functions

Example

The graph of f (x) =x2 − 2x− 3

x + 1:

f (x) =x2 − 2x− 3

x + 1=

(x− 3)(x + 1)(x + 1)

= x− 3 if x 6= 1

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 13 / 69

Graphs of Functions

Example

The graph of f (x) =x2 − 2x− 3

x + 1:

f (x) =x2 − 2x− 3

x + 1=

(x− 3)(x + 1)(x + 1)

= x− 3 if x 6= 1

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 13 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))

Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Graphs of Functions

Graphically:

Coordinates of a point on the graph in terms of x: (x, f (x))Domain: x-interval covered by the graph

Range: y-interval covered by the graph

Zero of a function: x-intercept of the graph

Intervals where the function value (or y-value) is positive: portions where thegraph lies above the x-axis

Intervals where the function value (or y-value) is negative: portions where thegraph lies below the x-axis

Math 53 (Part 1) Review of Functions 8 November 2012 14 / 69

Consider the graph of f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

(x, x− 3)

Domain:

R \ {−1}

Range:

R \ {−4}

Zero:

x = 3

Positive:

(3,+∞)

Negative:

(−∞,−1) ∪ (−1, 3)

Math 53 (Part 1) Review of Functions 8 November 2012 15 / 69

Consider the graph of f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

(x, x− 3)

Domain: R \ {−1}Range:

R \ {−4}

Zero:

x = 3

Positive:

(3,+∞)

Negative:

(−∞,−1) ∪ (−1, 3)

Math 53 (Part 1) Review of Functions 8 November 2012 15 / 69

Consider the graph of f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

(x, x− 3)

Domain: R \ {−1}Range: R \ {−4}Zero:

x = 3

Positive:

(3,+∞)

Negative:

(−∞,−1) ∪ (−1, 3)

Math 53 (Part 1) Review of Functions 8 November 2012 15 / 69

Consider the graph of f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

(x, x− 3)

Domain: R \ {−1}Range: R \ {−4}Zero: x = 3

Positive:

(3,+∞)

Negative:

(−∞,−1) ∪ (−1, 3)

Math 53 (Part 1) Review of Functions 8 November 2012 15 / 69

Consider the graph of f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

(x, x− 3)

Domain: R \ {−1}Range: R \ {−4}Zero: x = 3

Positive: (3,+∞)Negative:

(−∞,−1) ∪ (−1, 3)

Math 53 (Part 1) Review of Functions 8 November 2012 15 / 69

Consider the graph of f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

(x, x− 3)

Domain: R \ {−1}Range: R \ {−4}Zero: x = 3

Positive: (3,+∞)Negative: (−∞,−1) ∪ (−1, 3)

Math 53 (Part 1) Review of Functions 8 November 2012 15 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 16 / 69

Basic types of functions

Constant Functions - functions of the form f (x) = c, where c is a real number

dom f = R; ran f = {c}graph: horizontal line intersecting the y-axis at y = c

Math 53 (Part 1) Review of Functions 8 November 2012 17 / 69

Basic types of functions

Constant Functions - functions of the form f (x) = c, where c is a real number

dom f = R; ran f = {c}graph: horizontal line intersecting the y-axis at y = c

Math 53 (Part 1) Review of Functions 8 November 2012 17 / 69

Basic types of functions

ExampleConsider the constant function f (x) = 2.

−3 −2 −1 1 2 3

−1

1

2

3

0

Math 53 (Part 1) Review of Functions 8 November 2012 18 / 69

Basic types of functions

Linear Functions - functions of the form

f (x) = mx + b

with m 6= 0

dom f = R; ran f = R

graph: m is slope; y-intercept is b

Math 53 (Part 1) Review of Functions 8 November 2012 19 / 69

Basic types of functions

Linear Functions - functions of the form

f (x) = mx + b

with m 6= 0

dom f = R; ran f = R

graph: m is slope; y-intercept is b

Math 53 (Part 1) Review of Functions 8 November 2012 19 / 69

Basic types of functions

ExampleConsider the linear function f (x) = −x + 1.

−2 −1 1 2

−1

1

2

3

0

m = −1, y-intercept: 1

Math 53 (Part 1) Review of Functions 8 November 2012 20 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward, ran f =

[4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward, ran f =

[4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at

(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward, ran f =

[4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)

If a > 0: parabola opens upward, ran f =[

4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0:

parabola opens upward, ran f =[

4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward,

ran f =[

4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward, ran f =

[4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward, ran f =

[4ac−b2

4a ,+∞)

If a < 0:

parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Quadratic Functions - functions of the form

f (x) = ax2 + bx + c

with a 6= 0

dom f = R

graph: parabola with vertex at(− b

2a , 4ac−b2

4a

)If a > 0: parabola opens upward, ran f =

[4ac−b2

4a ,+∞)

If a < 0: parabola opens downward, ran f =(−∞, 4ac−b2

4a

]

Math 53 (Part 1) Review of Functions 8 November 2012 21 / 69

Basic types of functions

Example

Consider the quadratic function f (x) = x2.

−2 −1 1 2

1

2

3

4

0

A parabola opening upward with vertex at (0, 0)

Math 53 (Part 1) Review of Functions 8 November 2012 22 / 69

Basic types of functions

Example

Consider the quadratic function f (x) = −x2 − 2x + 3.

−3 −2 −1 1 2

−2

−1

1

2

3

4

0

A parabola opening downward with vertex at (−1, 4)

Math 53 (Part 1) Review of Functions 8 November 2012 23 / 69

Basic types of functions

Extreme function values of a quadratic function:

a > 0: f has a minimum function valuea < 0: f has a maximum function value

The extreme function value of f occurs at x = − b2a and the extreme function

value of f is f(− b

2a

)= 4ac−b2

4a

Math 53 (Part 1) Review of Functions 8 November 2012 24 / 69

Basic types of functions

Example

Consider the quadratic function f (x) = −x2 − 2x + 3.

Since a < 0

f has a maximum function value which occurs at x = −1The maximum value of f (x) is f (−1) = 4

Math 53 (Part 1) Review of Functions 8 November 2012 25 / 69

Basic types of functions

Example

Consider the quadratic function f (x) = −x2 − 2x + 3.

Since a < 0

f has a maximum function value which occurs at x = −1The maximum value of f (x) is f (−1) = 4

Math 53 (Part 1) Review of Functions 8 November 2012 25 / 69

Basic types of functions

Example

Consider the quadratic function f (x) = −x2 − 2x + 3.

Since a < 0

f has a maximum function value which occurs at x = −1The maximum value of f (x) is f (−1) = 4

Math 53 (Part 1) Review of Functions 8 November 2012 25 / 69

Basic types of functions

Polynomial Functions - functions of the form

f (x) = anxn + an−1xn−1 + · · ·+ a1x + a0

where n ∈W, an, an−1, ..., a0 are real numbers, with an 6= 0.

leading coefficient: an

degree of f : ndom f = R

Constant, linear and quadratic functions are special types of polynomialfunctions

Graphs of polynomial functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 26 / 69

Basic types of functions

Polynomial Functions - functions of the form

f (x) = anxn + an−1xn−1 + · · ·+ a1x + a0

where n ∈W, an, an−1, ..., a0 are real numbers, with an 6= 0.

leading coefficient: an

degree of f : n

dom f = R

Constant, linear and quadratic functions are special types of polynomialfunctions

Graphs of polynomial functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 26 / 69

Basic types of functions

Polynomial Functions - functions of the form

f (x) = anxn + an−1xn−1 + · · ·+ a1x + a0

where n ∈W, an, an−1, ..., a0 are real numbers, with an 6= 0.

leading coefficient: an

degree of f : ndom f = R

Constant, linear and quadratic functions are special types of polynomialfunctions

Graphs of polynomial functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 26 / 69

Basic types of functions

Polynomial Functions - functions of the form

f (x) = anxn + an−1xn−1 + · · ·+ a1x + a0

where n ∈W, an, an−1, ..., a0 are real numbers, with an 6= 0.

leading coefficient: an

degree of f : ndom f = R

Constant, linear and quadratic functions are special types of polynomialfunctions

Graphs of polynomial functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 26 / 69

Basic types of functions

Polynomial Functions - functions of the form

f (x) = anxn + an−1xn−1 + · · ·+ a1x + a0

where n ∈W, an, an−1, ..., a0 are real numbers, with an 6= 0.

leading coefficient: an

degree of f : ndom f = R

Constant, linear and quadratic functions are special types of polynomialfunctions

Graphs of polynomial functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 26 / 69

Basic types of functions

Rational Functions - functions of the form f (x) =p(x)q(x)

, where p and q are

polynomial functions, and q is not the constant zero function.

Domain: {x ∈ R | q(x) 6= 0}Graphs of rational functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 27 / 69

Basic types of functions

Rational Functions - functions of the form f (x) =p(x)q(x)

, where p and q are

polynomial functions, and q is not the constant zero function.

Domain: {x ∈ R | q(x) 6= 0}Graphs of rational functions: Unit 3

Math 53 (Part 1) Review of Functions 8 November 2012 27 / 69

Graphs of Functions

Example

Consider the rational function f (x) =x2 − 2x− 3

x + 1.

−3 −2 −1 1 2 3 4

−5

−4

−3

−2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 28 / 69

Basic types of functions

Functions involving rational exponents or radicals - functions of the form

f (x) = n√

x = x1/n

n is odd: dom f = R

n is even: dom f = [0, ∞)

Math 53 (Part 1) Review of Functions 8 November 2012 29 / 69

Basic types of functions

Functions involving rational exponents or radicals - functions of the form

f (x) = n√

x = x1/n

n is odd: dom f = R

n is even: dom f = [0, ∞)

Math 53 (Part 1) Review of Functions 8 November 2012 29 / 69

Basic types of functions

ExampleSquare root function: f (x) =

√x

y =√

x =⇒ y2 = x, y ≥ 0

1 2 3 4

−2

−1

1

2

0

The graph of x = y2

1 2 3 4

−2

−1

1

2

0

The graph of y =√

x

The graph of f (x) =√

x is the upper branch of the parabola x = y2

Math 53 (Part 1) Review of Functions 8 November 2012 30 / 69

Basic types of functions

ExampleSquare root function: f (x) =

√x

y =√

x =⇒ y2 = x, y ≥ 0

1 2 3 4

−2

−1

1

2

0

The graph of x = y2

1 2 3 4

−2

−1

1

2

0

The graph of y =√

x

The graph of f (x) =√

x is the upper branch of the parabola x = y2

Math 53 (Part 1) Review of Functions 8 November 2012 30 / 69

Basic types of functions

ExampleSquare root function: f (x) =

√x

y =√

x =⇒ y2 = x, y ≥ 0

1 2 3 4

−2

−1

1

2

0

The graph of x = y2

1 2 3 4

−2

−1

1

2

0

The graph of y =√

x

The graph of f (x) =√

x is the upper branch of the parabola x = y2

Math 53 (Part 1) Review of Functions 8 November 2012 30 / 69

Basic types of functions

Trigonometric/Circular Functions

sine, cosine, tangent, cotangent, secant and cosecant functions

In Math 53, the trigonometric functions are viewed as functions on the set ofreal numbers.

Math 53 (Part 1) Review of Functions 8 November 2012 31 / 69

Basic types of functions

Trigonometric/Circular Functions

sine, cosine, tangent, cotangent, secant and cosecant functions

In Math 53, the trigonometric functions are viewed as functions on the set ofreal numbers.

Math 53 (Part 1) Review of Functions 8 November 2012 31 / 69

Basic types of functions

Examplef (x) = sin x

−π−2π π 2π 3π 4π− π2− 3π

2π2

3π2

5π2

7π2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 32 / 69

Basic types of functions

Examplef (x) = cos x

−π−2π π 2π 3π 4π− π2− 3π

2π2

3π2

5π2

7π2

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 33 / 69

Basic Types of Functions

Examplef (x) = tan x

−π π 2π− π2− 3π

2π2

3π2

5π2

Math 53 (Part 1) Review of Functions 8 November 2012 34 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 35 / 69

Constructing a table of signs

The table of signs show when a given mathematical expression is positive, zero ornegative.

Two Methods:

1 Interval Method

2 Test Value Method

In both cases, one must determine the numbers where the given mathematicalexpression is zero or undefined.

Math 53 (Part 1) Review of Functions 8 November 2012 36 / 69

Constructing a table of signs

The table of signs show when a given mathematical expression is positive, zero ornegative.

Two Methods:

1 Interval Method

2 Test Value Method

In both cases, one must determine the numbers where the given mathematicalexpression is zero or undefined.

Math 53 (Part 1) Review of Functions 8 November 2012 36 / 69

Constructing a table of signs

The table of signs show when a given mathematical expression is positive, zero ornegative.

Two Methods:

1 Interval Method

2 Test Value Method

In both cases, one must determine the numbers where the given mathematicalexpression is zero or undefined.

Math 53 (Part 1) Review of Functions 8 November 2012 36 / 69

Constructing a table of signs

Example

Determine the intervals where the the graph of f (x) =2x2 − x3

2x2 − 3x + 1lies above

the x-axis.

We want to determine the intervals for which

2x2 − x3

2x2 − 3x + 1> 0

Math 53 (Part 1) Review of Functions 8 November 2012 37 / 69

Constructing a table of signs

Example

Determine the intervals where the the graph of f (x) =2x2 − x3

2x2 − 3x + 1lies above

the x-axis.

We want to determine the intervals for which

2x2 − x3

2x2 − 3x + 1

> 0

Math 53 (Part 1) Review of Functions 8 November 2012 37 / 69

Constructing a table of signs

Example

Determine the intervals where the the graph of f (x) =2x2 − x3

2x2 − 3x + 1lies above

the x-axis.

We want to determine the intervals for which

2x2 − x3

2x2 − 3x + 1> 0

Math 53 (Part 1) Review of Functions 8 November 2012 37 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1

=x2(2− x)

(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2

+ + + + +

2x− 1

− − + + +

x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2

+ + + + +

2x− 1

− − + + +

x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2

+ + + + +

2x− 1

− − + + +

x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2

+ + + + +

2x− 1

− − + + +

x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1

− − + + +

x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − −

+ + +

x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1

− − − + +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − −

+ +

2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x

+ + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + +

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+

+ − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+ +

− + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+ + −

+ −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − +

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signsInterval Method: rewrite the expression as a product of factors whose table ofsigns are easily determined.

2x2 − x3

2x2 − 3x + 1=

x2(2− x)(2x− 1)(x− 1)

Zero at: x = 0, 2, Undefined at: x = 12 , 1

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2 + + + + +2x− 1 − − + + +x− 1 − − − + +2− x + + + + −

x2(2− x)(2x− 1)(x− 1)

+ + − + −

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 38 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + − + −

Sample point in (−∞, 0): x = −1

(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+

+ − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+

+ − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):

(+)(+)

(−)(−)We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+

+ − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)

We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ +

− + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)

We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + −

+ −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)

We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + − +

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)

We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)

We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Test Value Method: test a value in the specified interval

(−∞, 0)(

0, 12

) (12 , 1)

(1, 2) (2,+∞)

x2(2− x)(2x− 1)(x− 1)

+ + − + −

Sample point in (−∞, 0): x = −1(−1)2(3)(−3)(−2)

Sample point in(

0, 12

):(+)(+)

(−)(−)We get the same result:

The graph of f lies above the x-axis in the intervals (−∞, 0) ∪(

0, 12

)∪ (1, 2).

Math 53 (Part 1) Review of Functions 8 November 2012 39 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ − + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ − + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ − + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1

+ − + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+

− + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ −

+ −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ − +

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ − + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Constructing a table of signs

Example

Find the domain of f (x) =√−5x

x2 − 1.

Domain: x ∈ R such that−5x

x2 − 1≥ 0

Zero at: x = 0, Undefined at: x = −1, 1

(−∞,−1) (−1, 0) (0, 1) (1,+∞)−5x

x2 − 1+ − + −

Therefore,dom f = (∞,−1) ∪ [0, 1)

Math 53 (Part 1) Review of Functions 8 November 2012 40 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 41 / 69

Piecewise-defined functions

Piecewise-defined functions are functions that are defined by more than oneexpression. Such functions can be written in the form

f (x) =

f1(x) if x ∈ X1f2(x) if x ∈ X2

... if...

fn(x) if x ∈ Xn

where X1, ..., Xn ⊆ R with Xi ∩ Xj = ∅ for all i 6= j.

Math 53 (Part 1) Review of Functions 8 November 2012 42 / 69

Piecewise-defined functions

ExampleAn example of a piecewise function is the signum function (or sign function),denoted by sgn and defined by

sgn x =

−1 if x < 00 if x = 01 if x > 0

−3 −2 −1 1 2 3

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 43 / 69

Piecewise-defined functions

ExampleAn example of a piecewise function is the signum function (or sign function),denoted by sgn and defined by

sgn x =

−1 if x < 00 if x = 01 if x > 0

−3 −2 −1 1 2 3

−1

1

0

Math 53 (Part 1) Review of Functions 8 November 2012 43 / 69

The Absolute Value Function

Absolute Value Function - denoted by |x| and defined by

|x| =√

x2 =

{x, x ≥ 0−x, x < 0

Math 53 (Part 1) Review of Functions 8 November 2012 44 / 69

The Absolute Value Function

The graph of f (x) = |x|

−3 −2 −1 1 2 3

1

2

3

0

Math 53 (Part 1) Review of Functions 8 November 2012 45 / 69

The Greatest Integer Function

Greatest Integer Function (GIF)

[[x]]: greatest integer less than or equal to x

Example

1 [[2.4]]

= 2

2 [[2]]

= 2

3 [[0]]

= 0

4 [[−2.1]]

= −3

5 [[−π]]

= −4

Math 53 (Part 1) Review of Functions 8 November 2012 46 / 69

The Greatest Integer Function

Greatest Integer Function (GIF)

[[x]]: greatest integer less than or equal to x

Example

1 [[2.4]] = 22 [[2]]

= 2

3 [[0]]

= 0

4 [[−2.1]]

= −3

5 [[−π]]

= −4

Math 53 (Part 1) Review of Functions 8 November 2012 46 / 69

The Greatest Integer Function

Greatest Integer Function (GIF)

[[x]]: greatest integer less than or equal to x

Example

1 [[2.4]] = 22 [[2]] = 23 [[0]]

= 0

4 [[−2.1]]

= −3

5 [[−π]]

= −4

Math 53 (Part 1) Review of Functions 8 November 2012 46 / 69

The Greatest Integer Function

Greatest Integer Function (GIF)

[[x]]: greatest integer less than or equal to x

Example

1 [[2.4]] = 22 [[2]] = 23 [[0]] = 04 [[−2.1]]

= −3

5 [[−π]]

= −4

Math 53 (Part 1) Review of Functions 8 November 2012 46 / 69

The Greatest Integer Function

Greatest Integer Function (GIF)

[[x]]: greatest integer less than or equal to x

Example

1 [[2.4]] = 22 [[2]] = 23 [[0]] = 04 [[−2.1]] = −35 [[−π]]

= −4

Math 53 (Part 1) Review of Functions 8 November 2012 46 / 69

The Greatest Integer Function

Greatest Integer Function (GIF)

[[x]]: greatest integer less than or equal to x

Example

1 [[2.4]] = 22 [[2]] = 23 [[0]] = 04 [[−2.1]] = −35 [[−π]] = −4

Math 53 (Part 1) Review of Functions 8 November 2012 46 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1,

− 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x

< 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 0

0, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00,

0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x

< 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 1

1, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 2

2, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3

......

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3...

...

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3...

...

In general,

[[x]] = n,

for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3...

...

In general,

[[x]] = n, for

n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3...

...

In general,

[[x]] = n, for n ≤ x

< n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer Function

As a piecewise function:

[[x]] =

......

− 1, − 1 ≤ x < 00, 0 ≤ x < 11, 1 ≤ x < 22, 2 ≤ x < 3...

...

In general,

[[x]] = n, for n ≤ x < n + 1 where n ∈ Z

Math 53 (Part 1) Review of Functions 8 November 2012 47 / 69

The Greatest Integer FunctionThe graph of f (x) = [[x]]

−4 −3 −2 −1 1 2 3 4

−4

−3

−2

−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 48 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 49 / 69

Operations on Functions

Definition (Operations on Functions)Let f and g be functions, c ∈ R.

1 Addition: ( f + g)(x) = f (x) + g(x); dom( f + g) = dom f ∩ dom g2 Subtraction: ( f − g)(x) = f (x)− g(x); dom( f − g) = dom f ∩ dom g3 Multiplication: ( f g)(x) = f (x)g(x); dom( f g) = dom f ∩ dom g

4 Division:(

fg

)(x) =

f (x)g(x)

;

dom(

fg

)= (dom f ∩ dom g) \ {x ∈ dom g | g(x) = 0}

5 Composition: ( f ◦ g)(x) = f (g(x));dom( f ◦ g) = {x ∈ dom g | g(x) ∈ dom f }

6 Scalar Multiplication: c f (x) = c ( f (x)); dom c f = dom f

Math 53 (Part 1) Review of Functions 8 November 2012 50 / 69

Operations on Functions

Example

Express the function F(x) = sin2 (3x− 1) as a composition of three functionslisted among the basic types of functions.

Let

f (x) = x2

g(x) = sin xh(x) = 3x− 1

ThenF(x) = ( f ◦ g ◦ h) (x)

Math 53 (Part 1) Review of Functions 8 November 2012 51 / 69

Operations on Functions

Example

Express the function F(x) = sin2 (3x− 1) as a composition of three functionslisted among the basic types of functions.

Let

f (x) = x2

g(x) = sin xh(x) = 3x− 1

ThenF(x) = ( f ◦ g ◦ h) (x)

Math 53 (Part 1) Review of Functions 8 November 2012 51 / 69

Operations on Functions

Example

Express the function F(x) = sin2 (3x− 1) as a composition of three functionslisted among the basic types of functions.

Let

f (x) = x2

g(x) = sin xh(x) = 3x− 1

ThenF(x) = ( f ◦ g ◦ h) (x)

Math 53 (Part 1) Review of Functions 8 November 2012 51 / 69

Operations on Functions

Example

Express the function F(x) = sin2 (3x− 1) as a composition of three functionslisted among the basic types of functions.

Let

f (x) = x2

g(x) = sin x

h(x) = 3x− 1

ThenF(x) = ( f ◦ g ◦ h) (x)

Math 53 (Part 1) Review of Functions 8 November 2012 51 / 69

Operations on Functions

Example

Express the function F(x) = sin2 (3x− 1) as a composition of three functionslisted among the basic types of functions.

Let

f (x) = x2

g(x) = sin xh(x) = 3x− 1

ThenF(x) = ( f ◦ g ◦ h) (x)

Math 53 (Part 1) Review of Functions 8 November 2012 51 / 69

Operations on Functions

Example

Express the function F(x) = sin2 (3x− 1) as a composition of three functionslisted among the basic types of functions.

Let

f (x) = x2

g(x) = sin xh(x) = 3x− 1

ThenF(x) = ( f ◦ g ◦ h) (x)

Math 53 (Part 1) Review of Functions 8 November 2012 51 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)]

=1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h

= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = x2 and g(x) = x + h. Find1h[( f ◦ g) (x)− f (x)].

1h[( f ◦ g) (x)− f (x)] =

1h[ f (g(x))− f (x)]

=f (x + h)− f (x)

h

=(x + h)2 − x2

h

=(x2 + 2xh + h2)− x2

h

=2xh + h2

h= 2x + h

Math 53 (Part 1) Review of Functions 8 November 2012 52 / 69

Operations on Functions

Example

Let f (x) = |x| and g(x) = x2 − 1. Express ( f ◦ g) (x) as a piecewise function.

Recall:

|x| =√

x2 =

{x, x ≥ 0−x, x < 0

Therefore,

( f ◦ g) (x) = f (g(x)) = |x2 − 1| ={

x2 − 1, x2 − 1 ≥ 0−(x2 − 1), x2 − 1 < 0

Math 53 (Part 1) Review of Functions 8 November 2012 53 / 69

Operations on Functions

Example

Let f (x) = |x| and g(x) = x2 − 1. Express ( f ◦ g) (x) as a piecewise function.

Recall:

|x| =√

x2 =

{x, x ≥ 0−x, x < 0

Therefore,

( f ◦ g) (x) = f (g(x)) = |x2 − 1| ={

x2 − 1, x2 − 1 ≥ 0−(x2 − 1), x2 − 1 < 0

Math 53 (Part 1) Review of Functions 8 November 2012 53 / 69

Operations on Functions

Example

Let f (x) = |x| and g(x) = x2 − 1. Express ( f ◦ g) (x) as a piecewise function.

Recall:

|x| =√

x2 =

{x, x ≥ 0−x, x < 0

Therefore,

( f ◦ g) (x) = f (g(x)) = |x2 − 1| ={

x2 − 1, x2 − 1 ≥ 0−(x2 − 1), x2 − 1 < 0

Math 53 (Part 1) Review of Functions 8 November 2012 53 / 69

Operations on Functions

Example

Let f (x) = |x| and g(x) = x2 − 1. Express ( f ◦ g) (x) as a piecewise function.

( f ◦ g) (x) = f (g(x)) = |x2 − 1| ={

x2 − 1, x2 − 1 ≥ 0−(x2 − 1), x2 − 1 < 0

(−∞,−1) (−1, 1) (1,+∞)

x− 1 − − +

x + 1 − + +

x2 − 1 + − +

( f ◦ g) (x) = |x2 − 1| ={

x2 − 1, x ≥ 1 or x ≤ 11− x2, −1 < x < 1

Math 53 (Part 1) Review of Functions 8 November 2012 54 / 69

Operations on Functions

Example

Let f (x) = |x| and g(x) = x2 − 1. Express ( f ◦ g) (x) as a piecewise function.

( f ◦ g) (x) = f (g(x)) = |x2 − 1| ={

x2 − 1, x2 − 1 ≥ 0−(x2 − 1), x2 − 1 < 0

(−∞,−1) (−1, 1) (1,+∞)

x− 1 − − +

x + 1 − + +

x2 − 1 + − +

( f ◦ g) (x) = |x2 − 1| ={

x2 − 1, x ≥ 1 or x ≤ 11− x2, −1 < x < 1

Math 53 (Part 1) Review of Functions 8 November 2012 54 / 69

Operations on Functions

Example

Let f (x) = |x| and g(x) = x2 − 1. Express ( f ◦ g) (x) as a piecewise function.

( f ◦ g) (x) = f (g(x)) = |x2 − 1| ={

x2 − 1, x2 − 1 ≥ 0−(x2 − 1), x2 − 1 < 0

(−∞,−1) (−1, 1) (1,+∞)

x− 1 − − +

x + 1 − + +

x2 − 1 + − +

( f ◦ g) (x) = |x2 − 1| ={

x2 − 1, x ≥ 1 or x ≤ 11− x2, −1 < x < 1

Math 53 (Part 1) Review of Functions 8 November 2012 54 / 69

( f ◦ g) (x) = |x2 − 1| ={

x2 − 1, x ≥ 1 or x ≤ 11− x2, −1 < x < 1

−3 −2 −1 1 2 3

1

2

3

Math 53 (Part 1) Review of Functions 8 November 2012 55 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n if n ≤ 2x + 1 < n + 1

n ≤ 2x + 1 < n + 1n− 1 ≤ 2x < nn− 1

2≤ x <

n2

Math 53 (Part 1) Review of Functions 8 November 2012 56 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n

if n ≤ 2x + 1 < n + 1

n ≤ 2x + 1 < n + 1n− 1 ≤ 2x < nn− 1

2≤ x <

n2

Math 53 (Part 1) Review of Functions 8 November 2012 56 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n if n ≤ 2x + 1 < n + 1

n ≤ 2x + 1 < n + 1n− 1 ≤ 2x < nn− 1

2≤ x <

n2

Math 53 (Part 1) Review of Functions 8 November 2012 56 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n if n ≤ 2x + 1 < n + 1

n ≤ 2x + 1 < n + 1

n− 1 ≤ 2x < nn− 1

2≤ x <

n2

Math 53 (Part 1) Review of Functions 8 November 2012 56 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n if n ≤ 2x + 1 < n + 1

n ≤ 2x + 1 < n + 1n− 1 ≤ 2x < n

n− 12

≤ x <n2

Math 53 (Part 1) Review of Functions 8 November 2012 56 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n if n ≤ 2x + 1 < n + 1

n ≤ 2x + 1 < n + 1n− 1 ≤ 2x < nn− 1

2≤ x <

n2

Math 53 (Part 1) Review of Functions 8 November 2012 56 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n, ifn− 1

2≤ x <

n2

[[2x + 1]] =

......

−1, if −1 ≤ x < − 12

0, if − 12 ≤ x < 0

1, if 0 ≤ x < 12

2, if 12 ≤ x < 1

......

Math 53 (Part 1) Review of Functions 8 November 2012 57 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n, ifn− 1

2≤ x <

n2

[[2x + 1]] =

......

−1, if −1 ≤ x < − 12

0, if − 12 ≤ x < 0

1, if 0 ≤ x < 12

2, if 12 ≤ x < 1

......

Math 53 (Part 1) Review of Functions 8 November 2012 57 / 69

Operations on Functions

ExampleLet f (x) = 2x + 1 and g(x) = [[x]]. Express (g ◦ f ) (x) as a piecewise function.

(g ◦ f ) (x) = [[2x + 1]] = n, ifn− 1

2≤ x <

n2

[[2x + 1]] =

......

−1, if −1 ≤ x < − 12

0, if − 12 ≤ x < 0

1, if 0 ≤ x < 12

2, if 12 ≤ x < 1

......

Math 53 (Part 1) Review of Functions 8 November 2012 57 / 69

−4 −3 −2 −1 1 2 3 4

−4

−3

−2

−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 58 / 69

Other Graphing Examples

Example

Graph g(x) =√

2− x.

y =√

2− x

y2 = 2− x, y ≥ 0

x = 2− y2, y ≥ 0

The graph of g is the upper branch of the parabola x = 2− y2.

Math 53 (Part 1) Review of Functions 8 November 2012 59 / 69

Other Graphing Examples

Example

Graph g(x) =√

2− x.

y =√

2− x

y2 = 2− x, y ≥ 0

x = 2− y2, y ≥ 0

The graph of g is the upper branch of the parabola x = 2− y2.

Math 53 (Part 1) Review of Functions 8 November 2012 59 / 69

Other Graphing Examples

Example

Graph g(x) =√

2− x.

y =√

2− x

y2 = 2− x, y ≥ 0

x = 2− y2, y ≥ 0

The graph of g is the upper branch of the parabola x = 2− y2.

Math 53 (Part 1) Review of Functions 8 November 2012 59 / 69

Other Graphing Examples

Example

Graph g(x) =√

2− x.

y =√

2− x

y2 = 2− x, y ≥ 0

x = 2− y2, y ≥ 0

The graph of g is the upper branch of the parabola x = 2− y2.

Math 53 (Part 1) Review of Functions 8 November 2012 59 / 69

Other Graphing Examples

Example

Graph g(x) =√

2− x.

y =√

2− x

y2 = 2− x, y ≥ 0

x = 2− y2, y ≥ 0

The graph of g is the upper branch of the parabola x = 2− y2.

Math 53 (Part 1) Review of Functions 8 November 2012 59 / 69

Other Graphing Examples

Example

Graph g(x) =√

2− x.

−2 −1 1 2

−2

−1

1

2

0

Math 53 (Part 1) Review of Functions 8 November 2012 60 / 69

Other Graphing Examples

Example

Graph h(x) = −√

4− x2.

y = −√

4− x2

y2 = 4− x2, y ≤ 0

x2 + y2 = 4, y ≤ 0

The graph of h is the lower semicircle of the circle x2 + y2 = 4.

Math 53 (Part 1) Review of Functions 8 November 2012 61 / 69

Other Graphing Examples

Example

Graph h(x) = −√

4− x2.

y = −√

4− x2

y2 = 4− x2, y ≤ 0

x2 + y2 = 4, y ≤ 0

The graph of h is the lower semicircle of the circle x2 + y2 = 4.

Math 53 (Part 1) Review of Functions 8 November 2012 61 / 69

Other Graphing Examples

Example

Graph h(x) = −√

4− x2.

y = −√

4− x2

y2 = 4− x2, y ≤ 0

x2 + y2 = 4, y ≤ 0

The graph of h is the lower semicircle of the circle x2 + y2 = 4.

Math 53 (Part 1) Review of Functions 8 November 2012 61 / 69

Other Graphing Examples

Example

Graph h(x) = −√

4− x2.

y = −√

4− x2

y2 = 4− x2, y ≤ 0

x2 + y2 = 4, y ≤ 0

The graph of h is the lower semicircle of the circle x2 + y2 = 4.

Math 53 (Part 1) Review of Functions 8 November 2012 61 / 69

Other Graphing Examples

Example

Graph h(x) = −√

4− x2.

y = −√

4− x2

y2 = 4− x2, y ≤ 0

x2 + y2 = 4, y ≤ 0

The graph of h is the lower semicircle of the circle x2 + y2 = 4.

Math 53 (Part 1) Review of Functions 8 November 2012 61 / 69

Other Graphing Examples

Example

Graph h(x) = −√

4− x2.

−2 −1 1 2

−2

−1

1

2

Math 53 (Part 1) Review of Functions 8 November 2012 62 / 69

Other Graphing Examples

Example

Graph f (x) =

x + 4 if x < −2

x3 + x2

x + 1if −2 ≤ x ≤ 2

|x− 6| if x > 2

.

f (x) =

x + 4 if x < −2

x2(x + 1)x + 1

if −2 ≤ x ≤ 2

−(x− 6) if 2 < x < 6x− 6 if x ≥ 6

f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

Math 53 (Part 1) Review of Functions 8 November 2012 63 / 69

Other Graphing Examples

Example

Graph f (x) =

x + 4 if x < −2

x3 + x2

x + 1if −2 ≤ x ≤ 2

|x− 6| if x > 2

.

f (x) =

x + 4 if x < −2

x2(x + 1)x + 1

if −2 ≤ x ≤ 2

−(x− 6) if 2 < x < 6x− 6 if x ≥ 6

f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

Math 53 (Part 1) Review of Functions 8 November 2012 63 / 69

Other Graphing Examples

Example

Graph f (x) =

x + 4 if x < −2

x3 + x2

x + 1if −2 ≤ x ≤ 2

|x− 6| if x > 2

.

f (x) =

x + 4 if x < −2

x2(x + 1)x + 1

if −2 ≤ x ≤ 2

−(x− 6) if 2 < x < 6x− 6 if x ≥ 6

f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

Math 53 (Part 1) Review of Functions 8 November 2012 63 / 69

Other Graphing Examples

The graph of f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

−5 −4 −3 −2 −1 1 2 3 4 5 6 7 8 9 10−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 64 / 69

Other Graphing Examples

The graph of f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

−5 −4 −3 −2 −1 1 2 3 4 5 6 7 8 9 10−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 64 / 69

Other Graphing Examples

The graph of f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

−5 −4 −3 −2 −1 1 2 3 4 5 6 7 8 9 10−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 64 / 69

Other Graphing Examples

The graph of f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

−5 −4 −3 −2 −1 1 2 3 4 5 6 7 8 9 10−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 64 / 69

Other Graphing Examples

The graph of f (x) =

x + 4 if x < −2

x2 if −2 ≤ x ≤ 2, x 6= −1−x + 6 if 2 < x < 6x− 6 if x ≥ 6

−5 −4 −3 −2 −1 1 2 3 4 5 6 7 8 9 10−1

1

2

3

4

0

Math 53 (Part 1) Review of Functions 8 November 2012 64 / 69

Outline

1 Functions

2 Basic Types of Functions

3 Constructing a table of signs

4 Piecewise-defined functions

5 Operations on Functions

6 Functions as Mathematical Models

Math 53 (Part 1) Review of Functions 8 November 2012 65 / 69

Functions as Mathematical Models

Express a certain situation as a functional relationship between certainquantities

Math 53 (Part 1) Review of Functions 8 November 2012 66 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the fieldThe area A of the field:

A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the field

The area A of the field:A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the fieldThe area A of the field:

A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the fieldThe area A of the field:

A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the fieldThe area A of the field:

A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240

y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the fieldThe area A of the field:

A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleA rectangular field has a perimeter of 240 meters. Express the area of the field asa function of its width.

Let x be the width and y be the length of the fieldThe area A of the field:

A = xy

Since the perimeter of the field is 240 meters:

2x + 2y = 240y = 120− x

The area of the field expressed as a function of x:

A(x) = x(120− x) = −x2 + 120x

Math 53 (Part 1) Review of Functions 8 November 2012 67 / 69

Functions as Mathematical Models

ExampleFind two numbers whose difference is 14 and whose product is minimum.

Let x be the greater number and y be the smaller number.Since the difference of 14 is positive

x− y = 14y = x− 14

The product as a function of x is

P(x) = x(x− 14) = x2 − 14x

P is a quadratic function with a minimum function value at

x = − b2a

= 7

The two numbers are 7 and −7, and the minimum product is P(7) = −49.

Math 53 (Part 1) Review of Functions 8 November 2012 68 / 69

Functions as Mathematical Models

ExampleFind two numbers whose difference is 14 and whose product is minimum.

Let x be the greater number and y be the smaller number.

Since the difference of 14 is positive

x− y = 14y = x− 14

The product as a function of x is

P(x) = x(x− 14) = x2 − 14x

P is a quadratic function with a minimum function value at

x = − b2a

= 7

The two numbers are 7 and −7, and the minimum product is P(7) = −49.

Math 53 (Part 1) Review of Functions 8 November 2012 68 / 69

Functions as Mathematical Models

ExampleFind two numbers whose difference is 14 and whose product is minimum.

Let x be the greater number and y be the smaller number.Since the difference of 14 is positive

x− y = 14y = x− 14

The product as a function of x is

P(x) = x(x− 14) = x2 − 14x

P is a quadratic function with a minimum function value at

x = − b2a

= 7

The two numbers are 7 and −7, and the minimum product is P(7) = −49.

Math 53 (Part 1) Review of Functions 8 November 2012 68 / 69

Functions as Mathematical Models

ExampleFind two numbers whose difference is 14 and whose product is minimum.

Let x be the greater number and y be the smaller number.Since the difference of 14 is positive

x− y = 14y = x− 14

The product as a function of x is

P(x) = x(x− 14) = x2 − 14x

P is a quadratic function with a minimum function value at

x = − b2a

= 7

The two numbers are 7 and −7, and the minimum product is P(7) = −49.

Math 53 (Part 1) Review of Functions 8 November 2012 68 / 69

Functions as Mathematical Models

ExampleFind two numbers whose difference is 14 and whose product is minimum.

Let x be the greater number and y be the smaller number.Since the difference of 14 is positive

x− y = 14y = x− 14

The product as a function of x is

P(x) = x(x− 14) = x2 − 14x

P is a quadratic function with a minimum function value at

x = − b2a

= 7

The two numbers are 7 and −7, and the minimum product is P(7) = −49.

Math 53 (Part 1) Review of Functions 8 November 2012 68 / 69

Functions as Mathematical Models

ExampleFind two numbers whose difference is 14 and whose product is minimum.

Let x be the greater number and y be the smaller number.Since the difference of 14 is positive

x− y = 14y = x− 14

The product as a function of x is

P(x) = x(x− 14) = x2 − 14x

P is a quadratic function with a minimum function value at

x = − b2a

= 7

The two numbers are 7 and −7, and the minimum product is P(7) = −49.Math 53 (Part 1) Review of Functions 8 November 2012 68 / 69

Announcements

Unit 1 Module will be available on 16 November 2012.

Google site: https://sites.google.com/a/math.upd.edu.ph/m53-s2-1213

All lecture slides will be posted in the website.

A printer–friendly, condensed version of slides for the 1st three lectures willbe uploaded in the website prior to the lecture.

Math 53 (Part 1) Review of Functions 8 November 2012 69 / 69

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