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Copyright © 2013, 2009, 2005 Pearson Education, Inc. 1

SOLVING EQUATIONS

SOLVING INEQUALITIES

TRANSPOSING FORMULA

Algebra

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Part 1Solving Equations

• Solving Linear, Quadratic, Cubic Equations

• Rational Equations• Equations with Radicals

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Check your understanding

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Equations

 An equation is a statement that twoexpressions are equal.

 x  + 2 =9 11 x  = 5 x  + 6 x    x 2  – 2 x   – 1 = 0

To solve an equation means to find all numbersthat make the equation a true statement. Thesenumbers are the solutions, or roots, of theequation. A number that is a solution of an

equation is said to satisfy  the equation, and thesolutions of an equation make up its solution set. Equations with the same solution set areequivalent equations.

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 Addition and MultiplicationProperties of Equality

Let a, b, and c  represent real numbers.

If a  = b, then a  + c  = b  + c .

That is, the same number may be

added to each side of an equationwithout changing the solution set.

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 Addition and Multiplication

Properties of Equality

Let a, b, and c  represent real numbers.

If  a  = b and c ≠ 0, then ac  = bc.

That is, each side of an equation may be

multiplied by the same nonzero numberwithout changing the solution set.

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Linear Equations

 A linear equation is also called a first-

degree equation since the greatest degree

of the variable is 1.

3 2 0 x  

2 5 x  

312

4 x  

1 8 x 

0.5( 3) 2 6 x x 

2 3 0.2 0 x x 

Linear

equations

Nonlinear

equations

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Solution 

SOLVING A LINEAR EQUATION

Solve 3(2 4) 7 ( 5). x x  3(2 4) 7 ( 5) x x 

6 12 7 5 x x 

6 12 2 x x  6 12 2 x  x    x  x    7 12 2 x  

1212 2   27   1 x       

7 14 x  

7

7 7

14,

 x    2 x  

Distributive property

Combine like terms. Add x  to each side.

Combine like terms.

 Add 12 to each side.

Combine like terms.

Divide each side

by 7.

Be carefulwith signs.

Example 1

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Exercise: Solve the equation.

1)

 Answer: (1) x = 6

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2 4 1 1 7

3 21

42 12

3

 x  x x 

SOLVING A LINEAR EQUATION

WITH FRACTIONS

Solve 2 4 1 1 7 .3 2 4 3

 x   x x 

Solution Multiply by 12, the

LCD of the fractions.

4(2 4) 6 3 28 x x x 

Distributive property

Distribute the 12 to all  

terms within

parentheses.

Example 2

Multiply.

2 4 1 1 73 2 4 3

12 12 12 12 x   x x 

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SOLVING A LINEAR EQUATION

WITH FRACTIONS

Solve

Solution 

14 16 3 28t t  Combine like terms.

11 44 x   Subtract 3 x ; subtract 16.

4 x   Divide each side by 11.

Example 2

8 16 6 3 28 x x x  Distributive property

2 4 1 1 7 .3 2 4 3

 x   x x 

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Quadratic Equations

• Solving Quadratic Equations by Factorization

• Solving Quadratic Equations Using the

Quadratic Formula• Solving Quadratic Equations by Completing

the Square

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Quadratic Equations

Method When the Method is Beneficial

1. Factoring Use when the quadratic equationcan be easily factored.

2. Completing the square Rarely the best method, but

important for future topics.

3. Quadratic formula Use when factoring is not easy, or possible, with integer coefficients.

Methods for Solving Quadratic Equations

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Example: Solving Quadratic Equations by

Factorization

2 3 18 0 x x

6 0 x

3 x

6 x 3 x

2 3 18 x x

6 x   0

3 0 x

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Solving Quadratic Equations Using the

Quadratic Formula

Using the Quadratic Formula

To solve a quadratic equation in the form

ax2

 +bx

 +c = 0, where

a0, use the quadraticformula:

2 4

2

b b ac x

a

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Example

• Solve using formula

2 4

2

b b ac x

a

22 7 3 0 x x

Solution The equation is in the form ax2 + bx + c = 0,

where a = 2, b = – 7, and c = 3.

27 7   2   34

22 x

 

7 49 24

4

 x 

7 254

 x  

7 5

4 x

 

7 5

4 x

 

  7 5

4 x

 

3 x   1

2

 x  

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Exercise

• Solve using formula

 Answer:

2 2 11 0 x x

2 48

2 x

 

2 4

2

b b ac x

a

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Solving Quadratic Equations by Completing

the Square

To solve a quadratic equation by completing the square:

1.  Write the equation in the form x2 + bx = c.

2.  Complete the square by adding (b/2)2 to both sides. 

3.  Write the completed square in factored form andsimplify the right side,

4.  Use the square root principle to eliminate the

square.

5.  Isolate the variable.

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Example:

Solve by completing the square.

Solution We first write the equation in the form

 x2 + bx = c.

2 10 16 0 x x

2 10 16 x x 2 10 25 16 25 x x

25 41 x

5 41 x

5 41 x

 Add 16 to both sides to get the form

 x 2 + bx  = c .

Complete the square by adding 25 to

both sides.

Factor.

Use the square root principle.

Subtract 5 from both sides to isolate x .

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Exercise:

Solve by completing the square2 12 9 13 x x

 Answer: 6 2 10 x

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Solving cubic equations.

Example:

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Long division of polynomials.

Example:

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Exercise: Solve the equations.

 Answer: x = 1, -0.382, -2.618-

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Exercise: Solve the equations.

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Rational Equations

A rational equation is an equation that has arational expression for one or more terms. To

solve a rational equation, multiply each side by

the least common denominator (LCD) of theterms of the equation and then solve the

resulting equation. Because a rational

expression is not defined when its denominator

is 0, 

proposed solutions for which any

denominator equals 0 are excluded from the

solution set.

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Example 3 SOLVING RATIONAL EQUATIONS THAT

LEAD TO LINEAR EQUATIONS

Solve each equation.

Solution 

3 1 2

3 1

 x x  x 

 x 

The least common denominator is 3( x – 1),

which is equal to 0 if x  = 1. Therefore, 1

cannot possibly be a solution of thisequation.

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Example 3 SOLVING RATIONAL EQUATIONS THAT

LEAD TO LINEAR EQUATIONS

Solution  3 1 23 1

 x x   x  x 

3( 1) 3( 1) 3( 13

)1 2

3 1

 x x  x  x 

 x 

 x x 

 

 

 Multiply by the LCD, 3( x – 1),

where x  ≠ 1.

( 1)(3 1) 3(2 ) 3 ( 1) x x x x x 

2 23 4 1 6 3 3 x x x x x  1 10 3 x x 

1 7 x 

Divide out common

factors.

Multiply.

Subtract 3 x 2; combine like

terms.

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Example 3 SOLVING RATIONAL EQUATIONS THAT

LEAD TO LINEAR EQUATIONS

Solution 1

7 x  

Proposed solution

1The solution set is .

7

The proposed solution meets the requirement

that x  ≠ 1 and does not cause any denominator

to equal 0. Substitute to check for correctalgebra.

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Example 4 SOLVING RATIONAL EQUATIONS THAT

LEAD TO LINEAR EQUATIONS

Solve each equation.

Solution 

22

2 2

 x 

 x x 

( 2) ( 2  2

) ( 2)22 2

 x 

 x x  x x x 

 

 

Multiply by the LCD, x – 2, where x  ≠ 2. 

2 2( 2) x x  Divide out common factors. 

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Example 4 SOLVING RATIONAL EQUATIONS THAT

LEAD TO LINEAR EQUATIONS

Solution 2 2 4 x x  Distributive property 

2 x  Solve the linear equation. 

2 x   Proposed solution.

The proposed solution is 2. However, the variable is

restricted to real numbers except 2. If x  = 2, then not only

does it cause a zero denominator, but multiplying by x – 2 in

the first step is multiplying both sides by 0, which is not

valid. Thus, the solution set is .0

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Example 5 SOLVING RATIONAL EQUATIONS THAT

LEAD TO QUADRATIC EQUATIONS

Solve each equation.

Solution 

2

3 2 1 2

2 2

 x 

 x x x x 

( 2)

3 2 1 2

2

 x 

 x x    x x 

Factor the last

denominator. 

3 2 1 22 ( 2)

( 2) ( 2) ( 2) x 

 x x  x x x x x x 

 x x     

Multiply by x ( x   – 2), x  ≠ 0, 2.

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Example 5 SOLVING RATIONAL EQUATIONS THAT

LEAD TO QUADRATIC EQUATIONS

Solution (3 2) ( 2) 2 x x x 

23 2 2 2 x x x  Distributive property

Divide out common factors.

23 3 0 x x  Standard form

3 ( 1) 0 x x   Factor.

3 0 x  

or 1 0 x   Zero-factor property

0 x   or 1 x   Proposed solutions

Because of the restriction x  ≠ 0, the only valid solution is  – 1.

The solution set is { – 1}.

Set each

factor equal

to 0.

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Exercise: Solve the equations.

2) a) b)

 Answer: (2) a) No solution, ø b) m = -4 (m = -1 cannot accept as

answer)

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Solving an Equation Involving

RadicalsStep 1 Isolate the radical on one side of the equation. 

Step 2   Raise each side of the equation to a power that

is the same as the index of the radical so that

the radical is eliminated. 

If the equation st i l l co ntains a radical, repeat

Steps 1 and 2.

Step 3 Solve the resulting equation. 

Step 4 Check each proposed solution in the original

equation. 

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Example 6 SOLVING AN EQUATION CONTAINING

A RADICAL (SQUARE ROOT)

Solve

Solution 

15 2 0. x x 

15 2 x x  Isolate the radical.

2

2 15 2 x x  Square each side.

2 15 2 x x  Solve the quadratic equation.

2 2 15 0 x x 

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Example 6 SOLVING AN EQUATION CONTAINING

A RADICAL (SQUARE ROOT)

Solve

Solution 

15 2 0. x x 

( 5)( 3) 0 x x  Factor.

5 0 x   or 3 0 x   Zero-factor property

5 x   or 3 x   Proposed solutions

Only 3 is a solution, so the solution set is {3}.

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Example 7 SOLVING AN EQUATION

CONTAINING TWO RADICALS

Solve

Solution When an equation contains tworadicals, begin by isolating one of the radicals

on one side of the equation.

2 3 1 1. x x 

2 3 1 1 x x 

2 3 1 1 x x  Square each side.

Isolate 2 3. x  

  2   2

12 3   1 x  x   

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Example 7 SOLVING AN EQUATION

CONTAINING TWO RADICALS

Solve

Solution

2 3 1 1. x x 

2   1)3   1 (2 1 x    x  x     

Don’t forget this

term when squaring.

Be careful!

1 2 1 x x  Isolate the

remaining

radical.

  22

1 2 1 x x  Square again.

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Example 7 SOLVING AN EQUATION

CONTAINING TWO RADICALS

Solution2 2 1 4( 1) x x x 

2 2 1 4 4 x x x  2 2 3 0 x x  Solve the quadratic equation.

( 3)( 1) 0 x x 

3 0 x 

    1 0 x 

  or3 x     1 x   or

Proposed solutions

 Apply the exponents.

Distributive property

Factor

Zero-factor property

Check each proposed solution in the original  equation. Both 3 and  – 1 are

solutions of the original equation, so { – 1,3} is the solution set.

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Exercises: Solve the equations.

3)

 Answer: (3) x = 5

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Part 2 Inequalities• Linear Inequalities

• Three-Part Inequalities• Quadratic Inequalities

• Rational Inequalities

• Absolute Value Equations and Inequalities

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Properties of Inequality

Let a, b and c  represent real numbers.

1. If a  < b , then a  + c  < b  + c .

2. If a  < b  and if c > 0, then ac  < bc .

3. If a  < b  and if c  < 0, then ac  > bc .

Replacing < with >, ≤ , or ≥ results in similar properties. 

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Linear Inequality in OneVariable

 A linear inequality in one variable is

an inequality that can be written in theform

where a and b are real numbers, with

a ≠ 0. (Any of the symbols ≥, <, and ≤may also be used.)

0,ax b

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Example 8 SOLVING A LINEAR INEQUALITY

Solve

Solution 

3 5 7. x 

3 5 7 x 

53 7   55 x  Subtract 5.

3 12 x 

3 12

3 3

 x 

Divide by – 3. Reverse

the direction of theinequality symbol

when multiplying or

dividing by a negative

number. 

Don’t forget toreverse the

symbol here.

4 x  

Combine like terms.

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Type ofInterval Set IntervalNotation Graph

Open

interval

{ x   x > a}

{ x  a < x < b}

{ x   x < b}

(a, )

(a, b)

( – , b)

Other

intervals

{ x   x ≥ a}

{ x  a < x ≤ b}

{ x  a ≤ x < b}

{ x   x≤ b}

[a, )

(a, b]

[a, b)

( – , b]

(

(  (

  (

a

a b

b

[a( ]a

b[ )a b

]b

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Type of

Interval

Set Interval

Notation

Graph

Closed

interval { x  a ≤ x ≤ b} [a, b]

Disjoint

interval { x   x  < a or x > b} ( – , a) 

(b, ) 

All realnumbers { x  x is a real number} ( – , )

[ ]

b

a b

a

(  (

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Example 9 SOLVING A LINEAR INEQUALITY

Solve 4 – 3 x  ≤ 7 + 2 x.  Give the solutionset in interval notation.

Solution 4 3 7 2 x x 

4 44 3 7 2 x x  Subtract 4.

3 3 2 x x 

3 32 22 x  x x    x  Subtract 2 x .

5 3 x 

Combine like terms.

Combine like terms.

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Example 9

Solve 4 – 3 x  ≤ 7 + 2 x.  Give the solutionset in interval notation.

Solution 

Divide by –5. Reverse thedirection of the inequality

symbol. 55

53

 x 

 x 

3

5 x  

3In interval notation the solution set is , .

5

03

5

[

SOLVING A LINEAR INEQUALITY

S f

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Exercises: Solve the following

1)

SOLVING A THREE PART

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Example 10 SOLVING A THREE-PART

INEQUALITY

Solution Solve  –

 

2 < 5 + 3 x  < 20.2 5 3 20 x 

52   5 55 3 20 x   Subtract 5 from

each part.

7 3 15 x  7 1

3 3

3 5

3

 x 

Divide each

part by 3.

75

3 x 

7The solution set is the interval ,5 .

3

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Quadratic Inequalities

 A quadratic inequality is an inequality

that can be written in the form2 0ax bx c  

for real numbers a, b, and c , with a ≠ 0.(The symbol < can be replaced with >,≤, or ≥.) 

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Solving a Quadratic Inequality

Step 1   Solve the corresponding quadratic

equation.Step 2   Identify the intervals determined by

the solutions of the equation.

Step 3   Use a test value from each interval

to determine which intervals formthe solution set.

SOLVING A QUADRATIC

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Example 11 SOLVING A QUADRATIC

INEQULITY

Solve

Solution 

2

12 0. x x 

Step 1 Find the values of x  that satisfy x 2  –  x   – 12 = 0. 

2 12 0 x x  Corresponding quadratic

equation

( 3)( 4) 0 x x  Factor.

3 0 x     4 0 x   or Zero-factor property

3 x     4 x  or Solve each equation.

SOLVING A QUADRATIC

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Example 11 SOLVING A QUADRATIC

INEQULITY

Step 2 The two numbers – 3 and 4 dividethe number line into three intervals. The

expression x 2  –  x   – 12 will take on a value

that is either less than  zero or greater than  zero on each of these intervals. 

 – 3 0 4

Interval A Interval B Interval C( –, – 3) ( – 3, 4) (4, )

-+ +

E l 11 SOLVING A QUADRATIC

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Example 11 SOLVING A QUADRATIC

INEQULITY

IntervalTest

Value

Is x 2 –  x  – 12 < 0 

True or False?

A: ( – , – 3)  – 4  ( – 4)2  –  ( – 4) – 12 < 0 ?

8 < 0 False 

B: ( – 3, 4) 0 02  –  0 – 12 < 0 ?

 – 12 < 0 True 

C: (4, )  5 52  –  5 – 12 < 0 ?

8 < 0 False 

Step 3 Choose a test value from each interval. 

Since the values in Interval B make the inequality

true, the solution set is ( – 3, 4).

E l 12 SOLVING A QUADRATIC

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Example 12 SOLVING A QUADRATIC

INEQUALITY

Solve

Solution 

2

2 5 12 0. x x 

Step 1 Find the values of x  that satisfy 

22 5 12 0 x x  Corresponding

quadratic equation

(2 3)( 4) 0 x x  Factor.

2 3 0 x   or 4 0 x   Zero-factor property

22 5 12 0. x x 

E l 12 SOLVING A QUADRATIC

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Example 12 SOLVING A QUADRATIC

INEQUALITY

SolveSolution 

2

2 5 12 0. x x 

Step 12 3 0 x   or 4 0 x  

32

 x   or 4 x   

Step 2   The values form the intervals on the

number line. 

 – 40

3/2

Interval A Interval B Interval C( –, – 4) ( – 4, 3/2) (3/2, )

+ +-

E l 12 SOLVING A QUADRATIC

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Example 12 SOLVING A QUADRATIC

INEQUALITY

Step3 Choose a test value from each interval. 

IntervalTest

Value

Is 2 x 2 + 5 x  –  12 ≥ 0True or False?

A: ( – , – 4)  – 5 2( – 5)2 +5( – 5) – 12 ≥ 0 ?

13 ≥ 0 True

B: ( – 4, 3/2) 0 2(0)2 +5(0) – 12 ≥ 0 ?

 – 12 ≥ 0 False

C: (3/2, )  2 2(2)2

 +  5(2) – 12 ≥ 0 ?6 ≥ 0 True 

The values in Intervals A and C make the inequality true, so

the solution set is the union of the intervals     3

, 4 , .2

 

E l 13 FINDING PROJECTILE HEIGHT

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Example 13 FINDING PROJECTILE HEIGHT

If a projectile is launched from ground levelwith an initial velocity of 96 ft per sec, its

height s in feet t  seconds after launching is

given by the following equation.216 96s t t 

When will the projectile be greater than 80 ft

above ground level?

E l 13 FINDING PROJECTILE HEIGHT

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Example 13 FINDING PROJECTILE HEIGHT

216 96   80t t  Set s greater than

80.

Solution 

216 96 80 0t t  Subtract 80.

2 6 5 0t t     Divide by  – 16.

Reverse the

direction of the

inequalitysymbol.

Now solve thecorresponding equation.

E l 13 FINDING PROJECTILE HEIGHT

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Example 13 FINDING PROJECTILE HEIGHT

2 6 5 0t t 

Solution 

( 1)( 5) 0t t  Factor.

1t  

Zero-factor property

or 5t   Solve each equation.

or1 0t     5 0t  

E ample 13 FINDING PROJECTILE HEIGHT

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Example 13 FINDING PROJECTILE HEIGHT

Solution 

Interval C

10 5

Interval A Interval B

( – , 1) (1, 5) (5, )

Use the procedure of Examples 5 and 6 to

determine that values in Interval B, (1, 5) ,

satisfy the inequality. The projectile is

greater than 80 ft above ground level

between 1 and 5 sec after it is launched.

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Solving a Rational Inequality

Step 1 Rewrite the inequality, if necessary, so that

0 is on one side and there is a single fraction on the

other side. 

Step 2 Determine the values that will cause either

the numerator or the denominator of the rational

expression to equal 0. These values determine the

intervals of the number line to consider. 

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Solving a Rational Inequality

Step 3 Use a test value from each interval to

determine which intervals form the solution set. 

 A value causing the denominator to equal zero will

never be included in the solution set. If the

inequality is strict, any value causing the numerator

to equal zero will be excluded. If the inequality isnonstrict, any such value will be included. 

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Caution  Solving a rational inequality such as5

14 x 

by multiplying each side by x  + 4 to obtain5 ≥ x  + 4 requires considering two cases, since

the sign of x  + 4 depends on the value of x . If

 x  + 4 is negative, then the inequality symbol

must be reversed. The procedure used in thenext two examples eliminates the need for

considering separate cases.

Example 14 SOLVING A RATIONAL

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Example 14

Solve

Solution 

51.4 x 

Step 1

5

1   04 x  Subtract 1 so that 0 ison one side.

450

4   4 x  x 

 x  

Use x + 4 as the

common denominator.

( )5 40

4

 x 

 x 

Write as a single fraction.

Note the

careful use

of

parentheses.

SOLVING A RATIONAL

INEQUALITY

Example 14 SOLVING A RATIONAL

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Example 14

Solution 

Step 1 14

0 x 

 x 

  Combine terms in thenumerator, being careful

with signs.

Step 2 The quotient possibly changes sign only where x -

values make the numerator or denominator 0. This occurs at1   0 x    or 4   0 x    

1 x   or 4 x  

SOLVING A RATIONAL

INEQUALITY

 – 40

1

1- x

X + 4

+- -

+- ++ -+

Example 14 SOLVING A RATIONAL

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Example 14

The values in the interval ( –4, 1) satisfy the

original inequality. The value 1 makes the

nonstrict inequality true, so it must be included

in the solution set. Since –4 makes thedenominator 0, it must be excluded. The

solution set is ( –4, 1].

SOLVING A RATIONAL

INEQUALITY

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Caution Be careful w ith the

endpo ints of the intervals when so lv ing

rat ional inequali t ies . 

Example 15 SOLVING A RATIONAL

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Example 15 SOLVING A RATIONAL

INEQUALITY

Solve

Solution 

2 15.3 4

 x 

 x 

2 15 0

3 4

 x 

 x 

Subtract 5.

2 1 5(3 4)0

3 4 3 4

 x x 

 x x 

Common denominator

is 3 x  + 4.

2 1 5(3 4)0

3 4

 x x 

 x 

Write as a single

fraction.

Example 15 SOLVING A RATIONAL

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Example 15

Solve

Solution 

2 15.3 4

 x 

 x 

013 21 x   

Set the numerator and denominator equal to

0 and solve the resulting equations to findthe values of x  where sign changes may

occur.

or 3 4   0 x     21

13 x   or

4

3 x  

SOLVING A RATIONAL

INEQUALITY

Example 15 SOLVING A RATIONAL

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Example 15

Solution 

-13x - 21

3x + 4

21

13

4

3

SOLVING A RATIONAL

INEQUALITY

Because of the < symbol, neither endpoint satisfies the inequality, so the

solution set is 21 4, , .

13 3

+-

-

--

+

-+

-

13 213

04 x 

 x  

Exercises: Solve the following

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Exercises: Solve the following

2)

 Answer: (2) Solution set:

Example 16 SOLVING A RATIONAL

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Example 16

Solve

Solution 

SOLVING A RATIONAL

INEQUALITY

Example 16 SOLVING A RATIONAL

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Example 16

Solution: Find all the possible values of x.

SOLVING A RATIONAL

INEQUALITY

x + 3x - 4

1 - x

-

--

-

+

++

-

-

- ++

+

+

+ -

 Answer:

Exercises: Solve the following

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Exercises: Solve the following

3)

 Answer: (3) Solution set:

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Hint You can wri te your answer in

inequal ity notat ion or in terval notat ion . 

Example:

Check your understanding

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Lina Kristin

Who is correct? Explain your reasoning.

Check your understanding

To solve inequations (Rational Functions)

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To solve inequations (Rational Functions) 

5

05

9

05

)5(4

015

4

15

4

CORRECT

 x

 x

 x

 x x

 x

 x

 x

 x

?????

54

15

4

WRONG

 x x

 x

 x

Absolute Value

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Absolute Value

For each equation or inequality in Cases 1-3 in the table,

assume that k  > 0.

In Cases 2 and 3, the strict inequality may be replaced by its

nonstrict form. Additionally, if an absolute value equation takesthe form │a │= │b │, then a and b must be equal in value or

opposite in value.

Thus, the equivalent form of │a │= │b │ is a = b or a = –b.

Absolute Value Inequality

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q y

Example 16 SOLVING ABSOLUTE VALUE

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Example 16EQUATIONS

Solve each equation.(a) 5 3 12 x 

Solution 

5 3 12 x 

5 3 12 x  or 5 3 12 x  Case 1

3 7 x  or 3 17 x  Subtract 5.

7

3 x   or

17

3 x   Divide by 

 – 3.The solution set is 7 17

, .3 3

Example 17 SOLVING ABSOLUTE VALUE

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Example 17EQUATIONS

Solve each equation.

(b) 4 3 6 x x 

Solution 

4 3 6 x x 

or 4 3 ( 6) x x 

3 9 x   or 4 3 6 x x 

3 x   or 5 3 x  

35

 x  

4 3 6 x x 

3The solution set is ,3 .

5

Example 18 SOLVING ABSOLUTE VALUE

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a p e 8INEQUALITIES

Solution 

(a)

Solve each inequality.

2 1 7 x  

This inequality fits Case 2.

2 1 7 x   7 2 1 7 x  Case 2

8 2 6 x  Subtract 1 from each part.

4 3 x  Divide each part by 2.

The final inequality gives the solution set ( – 4, 3).

Example 18 SOLVING ABSOLUTE VALUE

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pINEQUALITIES

Solution This inequality fits Case 3.

(b)Solve each inequality.2 1 7 x  

2 1 7 x  

2 1 7 x   Case 3

Subtract 1 from

each side.

Divide each part by 2.

or 2 1 7 x  

2 8 x 

  or 2 6 x  4 x   or 3 x  

The solution set is ( , 4) (3, ).

Example 19 SOLVING AN ABSOLUTE VALUE

INEQUALITY

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pINEQUALITY

SolveSolution 

2 7 1 4. x 

2 7 1 4 x 

2 7 5 x 

 Add 1 to each side.2 7 5 x  or 2 7 5 x  Case 3

7 7 x  or 7 3 x 

1 x   or3

7 x   

Subtract 2.

Divide by – 7.  Reverse

the direction of each

inequality. 

  3

The solution set is , 1, .7

Example 20 SOLVING SPECIAL CASES

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p

Solve each equation or inequality.

Solution Since the absolute value of anumber is always nonnegative, the inequality

is always true. The solution set includes allreal numbers, written ( –∞,∞). 

2 5 4 x  (a)

Solution There is no number whoseabsolute value is less than – 3 (or less thanany  negative number). The solution set is  . 

(b) 4 7 3 x  

0

Example 20 SOLVING SPECIAL CASES

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p

Solve each equation or inequality.

Solution The absolute value of a number

will be 0 only if that number is 0. Therefore,

5 15 0 x   (c)

5 15 0 x   is equivalent to 5 15 0 x  

which has solution set { – 3}. Check by

substituting into the original equation.

Exercises: Solve the following

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4)

 Answer:(4) Solution set:

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Part 3 Transposing formula• A formula may have several variables,

represented by symbols and we can solve onevariable if we know the values of the other

variables.

•Rearranging a formula to change the subject is

called transposition.

Example 21 Solve the value of unknown

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p

The volume of a circular cylinder is given

by the formula V = r 2h. Given that r =

2.5 cm and h =15.75 cm, find V correct

to 2 decimal places (Note that, V is thesubject of the formula)

Ans: 309.25cm3

Example 22 Transposing formula

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Solve for the specified variable. Use  when

taking square roots if needed.

Solution 

(a)2

, for4

d  A d 

2

4 A

  d  Goal: Isolate d ,

the specified

variable.

2

4 A   d  Multiply each side by 4.

24 Ad 

Divide each side by .

Example 22 Transposing formula

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Solution Square root property

4d    A

4 A

 

Multiply by .

  

  

4d 

  A

2

d   A

Multiply numerators.

Multiply denominators.

Simplify the radical.

Example 23 Transposing formula

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The formula gives the time

of swing of a simple pendulum of

length L. Transpose the formula to

make L the subject.

 g  Lt      2

Example 23 Transposing formula

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divided by 2    at bothsides

square both sides

multiply by g at both

sides

t  g  L   2

  2

 g 

 L

2

2   

  

 

  

 g 

 L

2

2   

  

 

  

t  g  L

 __

2    2 2

 __2    

g   x  x g

Solution 

What if we transpose the formula to

k th bj t?

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t  g 

 L

)2(     

  22

2   t  L  

  L g 

2

2  

g

make g  the subject?

Square both sides22

Multiply both sides by g

Exercises:

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Exercises:

Rearrange each of the following formulae tomake the quantity shown the subject.

Answers:

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Answers:

REVIEW EXERCISE

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1) Solve the rational inequality .01010

 x x

 Answer:

1) the solution is the set ( –, –10]  (10, ).

2) the solution is the set (-4 -11/3] [0 )

2) Solve the rational inequality . p

 p

 p3

4