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Georgia Department of Education

Accelerated Mathematics II

Frameworks Student Edition

Unit 2 Inverse and Polynomial

Functions

3rd Edition April, 2011

Georgia Department of Education

Georgia Department of Education Accelerated Mathematics II Unit 2 3rd Edition

Georgia Department of Education Dr. John D. Barge, State School Superintendent

April, 2011 • of 45 All Rights Reserved

Table of Contents INTRODUCTION: .................................................................................................. 3

Please Tell Me in Dollar and Cents Learning Task .............................................. 6

The Cantilever Learning Task..…………………………..…………………….14 Characteristics of Polynomial Functions Learning Task.…………...………..18 Program Evaluation Learning Task……………………………………………31 The Swimming Debate Learning Task..………………………...……………………..37




Accelerated Mathematics II – Unit 2 Inverse and Polynomial Functions

Student Edition

INTRODUCTION: The exploration of inverse functions leads to investigation of: the operation of function composition, the concept of one-to-one function, and methods for finding inverses of previously studied functions. ENDURING UNDERSTANDINGS:

• Functions with restricted domains can be combined to form a new function whose domain is the union of the functions to be combined as long as the function values agree for any input values at which the domains intersect.

• One-to-one functions have inverse functions. • The inverse of a function is a function that reverses, or “undoes” the action of the original

function. • The graphs of a function and its inverse function are reflections across the line y = x.

KEY STANDARDS ADDRESSED: MA2A2. Students will explore inverses of functions.

a. Discuss the characteristics of functions and their inverses, including one-to-oneness, domain, and range.

b. Determine inverses of linear, quadratic, and power functions and functions of the form

( ) af xx

= , including the use of restricted domains.

c. Explore the graphs of functions and their inverses. d. Use composition to verify that functions are inverses of each other.

MA2A3. Students will analyze graphs of polynomial functions of higher degree.

a. Graph simple polynomial functions as translations of the function f(x) = axn.

b. Understand the effects of the following on the graph of a polynomial function: degree, lead coefficient, and multiplicity of real zeros.

c. Determine whether a polynomial function has symmetry and whether it is even, odd, or neither.

MA2G5. Students will investigate planes and spheres. a. Plot the point (x, y, z) and understand it as a vertex of a rectangular prism. b. Apply the distance formula in 3-space.




RELATED STANDARDS ADDRESSED:

MA2P1. Students will solve problems (using appropriate technology). a. Build new mathematical knowledge through problem solving. b. Solve problems that arise in mathematics and in other contexts. c. Apply and adapt a variety of appropriate strategies to solve problems. d. Monitor and reflect on the process of mathematical problem solving. MA2P2. Students will reason and evaluate mathematical arguments. a. Recognize reasoning and proof as fundamental aspects of mathematics. b. Make and investigate mathematical conjectures. c. Develop and evaluate mathematical arguments and proofs. d. Select and use various types of reasoning and methods of proof. MA2P3. Students will communicate mathematically. a. Organize and consolidate their mathematical thinking through communication.

b. Communicate their mathematical thinking coherently and clearly to peers, teachers, and others.

c. Analyze and evaluate the mathematical thinking and strategies of others. d. Use the language of mathematics to express mathematical ideas precisely.

MA2P4. Students will make connections among mathematical ideas and to other disciplines.

a. Recognize and use connections among mathematical ideas. b. Understand how mathematical ideas interconnect and build on one another to produce a

coherent whole. c. Recognize and apply mathematics in contexts outside of mathematics.

MA2P5. Students will represent mathematics in multiple ways. a. Create and use representations to organize, record, and communicate mathematical ideas. b. Select, apply, and translate among mathematical representations to solve problems. c. Use representations to model and interpret physical, social, and mathematical

phenomena. Unit Overview: The first and second tasks focus on exploration of inverse functions. In the first task of the unit, conversions of temperatures among Fahrenheit, Celsius, and Kelvin scales and currency conversions among yen, pesos, Euros, and US dollars provide a context for introducing the concept of composition of functions. Reversing conversions is used as the context for introducing the concept of inverse function. Students explore finding inverses from verbal statements, tables of values, algebraic formulas, and graphs. In the second task, students explore one-to-oneness as the property necessary for a function to have an inverse and see how restricting the domain of a non-invertible function can create a related function that is invertible.




The last task introduces exponential functions and explores them through several applications to situations of growth: the spread of a rumor, compound interest, and continuously compounded interest. Students explore the graphs of exponential functions and apply transformations involving reflections, stretches, and shifts.




Please Tell Me in Dollar and Cents Learning Task 1. Aisha made a chart of the experimental data for her science project and showed it to her

science teacher. The teacher was complimentary of Aisha’s work but suggested that, for a science project, it would be better to list the temperature data in degrees Celsius rather than degrees Fahrenheit.

a. Aisha found the formula for converting from degrees Fahrenheit to degrees Celsius:

( )5 329

C F= − .

Use this formula to convert freezing (32°F) and boiling (212°F) to degrees Celsius.

b. Later Aisha found a scientific journal article related to her project and planned to use

information from the article on her poster for the school science fair. The article included temperature data in degrees Kelvin. Aisha talked to her science teacher again, and they concluded that she should convert her temperature data again – this time to degrees Kelvin. The formula for converting degrees Celsius to degrees Kelvin is

273K C= + . Use this formula and the results of part a to express freezing and boiling in degrees Kelvin.

c. Use the formulas from part a and part b to convert the following to °K: – 238°F,

5000°F .

In converting from degrees Fahrenheit to degrees Kelvin, you used two functions, the function for converting from degrees Fahrenheit to degrees Celsius and the function for converting from degrees Celsius to degrees Kelvin, and a procedure that is the key idea in an operation on functions called composition of functions. Composition of functions is defined as follows: If f and g are functions, the composite function f go (read this notation as “f composed with g) is the function with the formula

( ) ( )( ) ( )f g x f g x=o , where x is in the domain of g and g(x) is in the domain of f. 2. We now explore how the temperature conversions from Item 1, part c, provide an example of

a composite function. a. The definition of composition of functions indicates that we start with a value, x, and first

use this value as input to the function g. In our temperature conversion, we started with a temperature in degrees Fahrenheit and used the formula to convert to degrees Celsius, so




the function g should convert from Fahrenheit to Celsius: ( )5( ) 329

g x x= − . What is the

meaning of x and what is the meaning of g(x) when we use this notation?

b. In converting temperature from degrees Fahrenheit to degrees Kelvin, the second step is

converting a Celsius temperature to a Kelvin temperature. The function f should give us this conversion; thus, ( ) 273f x x= + . What is the meaning of x and what is the meaning of f (x) when we use this notation?

c. Calculate ( ) ( )(45) (45)f g f g=o . What is the meaning of this number?

d. Calculate ( ) ( )( ) ( )f g x f g x=o , and simplify the result. What is the meaning of x and

what is the meaning of ( ) ( )f g xo ?

e. Calculate ( ) ( )(45) (45)f g f g=o using the formula from part d. Does your answer agree with your calculation from part c?

f. Calculate ( ) ( )( ) ( )g f x g f x=o , and simplify the result. What is the meaning of x? What meaning, if any, relative to temperature conversion can be associated with the value of ( ) ( )g f xo ?

We now explore function composition further using the context of converting from one type of currency to another.

3. On the afternoon of May 3, 2009, each Japanese yen (JPY) was worth 0.138616 Mexican

pesos (MXN), each Mexican peso was worth 0.0547265 Euro (EUR), and each Euro was worth 1.32615 US dollars (USD).1

a. Using the rates above, write a function P such that P(x) is the number of Mexican pesos

equivalent to x Japanese yen.

b. Using the rates above, write a function E that converts from Mexican pesos to Euros.

1 Students may find it more interesting to look up current exchange values to use for this item and Item 9, which depends on it. There are many websites that provide rates of exchange for currency. Note that these rates change many times throughout the day, so it is impossible to do calculations with truly “current” exchange values. The values in Item 3 were found using http://www.xe.com/ucc/ .




c. Using the rates above, write a function D that converts from Euros to US dollars.

d. Using functions as needed from parts a – c above, what is the name of the composite

function that converts Japanese yen to Euros? Find a formula for this function. (Original values have six significant digits; use six significant digits in the answer.)

e. Using functions as needed from parts a – c above, what is the name of the composite

function that converts Mexican pesos to US dollars? Find a formula for this function. (Use six significant digits in the answer.)

f. Using functions as needed from parts a – c above, what is the name of the composite

function that converts Japanese yen to US dollars? Find a formula for this function. (Use six significant digits in the answer.)

g. Use the appropriate function(s) from parts a - f to find the value, in US dollars, of the following: 10,000 Japanese yen; 10,000 Mexican pesos; 10,000 Euros.

Returning to the story of Aisha and her science project; it turned out that Aisha’s project was selected to compete at the science fair for the school district. However, the judges made one suggestion – that Aisha express temperatures in degrees Celsius rather than degrees Kelvin. For her project data, Aisha just returned to the values she had calculated when she first converted from Fahrenheit to Celsius. However, she still needed to convert the temperatures in the scientific journal article from Kevin to Celsius. The next item explores the formula for converting from Kelvin back to Celsius. 4. Remember that the formula for converting from degrees Celsius to degrees Kelvin is

273K C= + . In Item 2, part b, we wrote this same formula by using the function f where ( )f x represents the Kelvin temperature corresponding to a temperature of x degrees Celsius. a. Find a formula for C in terms of K, that is, give a conversion formula for going from °K

to °C.

b. Write a function h such that ( )h x is the Celsius temperature corresponding to a

temperature of x degrees Kelvin.

c. Explain in words the process for converting from degrees Celsius to degrees Kelvin. Do

the equation 273K C= + and the function f from Item 2, part b both express this idea?




d. Explain verbally the process for converting form degrees Kelvin to degrees Celsius. Do

your formula from part a above and your function h from part b both express this idea?

e. Calculate the composite function h fo , and simplify your answer. What is the meaning of x when we use x as input to this function?

f. Calculate the composite function f ho , and simplify your answer. What is the meaning

of x when we use x as input to this function?

In working with the functions f and h in Item 4, when we start with an input number, apply one function, and then use the output from the first function as the input to the other function, the final output is the starting input number. Your calculations of h fo and f ho show that this happens for any choice for the number x. Because of this special relationship between f and h , the function h is called the inverse of the function f and we use the notation −1f (read this as “f inverse”) as another name for the function h. The precise definition for inverse functions is: If f and h are two functions such that

( ) ( )( ) ( )h f x h f x x= =o for each input x in the domain of f, and

( ) ( )( ) ( )f h x f h x x= =o for each input x in the domain of h, then h is the inverse of the function f, and we write h = 1f − . Also, f is the inverse of the

function h, and we can write f = 1h− . Note that the notation for inverse functions looks like the notation for reciprocals, but in the inverse function notation, the exponent of “–1 ” does not indicate a reciprocal. 5. Each of the following describes the action of a function f on any real number input. For each

part, describe in words the action of the inverse function, 1f − , on any real number input. Remember that the composite action of the two functions should get us back to the original input. a. Action of the function f : subtract ten from each input

Action of the function 1f − :




b. Action of the function f : add two-thirds to each input

Action of the function 1f − :

c. Action of the function f : multiply each input by one-half Action of the function 1f − :

d. Action of the function f : multiply each input by three-fifths and add eight Action of the function 1f − :

6. For each part of Item 5 above, write an algebraic rule for the function and then verify that the

rules give the correct inverse relationship by showing that ( )1 ( )f f x x− = and

( )1( )f f x x− = for any real number x.

Before proceeding any further, we need to point out that there are many functions that do not have an inverse function. We’ll learn how to test functions to see if they have an inverse in the next task. The remainder of this task focuses on functions that have inverses. A function that has an inverse function is called invertible. 7. The tables below give selected values for a function f and its inverse function 1f − .

a. Use the given values and the definition of inverse function to complete both tables.

b. For any point (a, b) on the graph of f, what is the corresponding point on the graph of

1−f ?

c. For any point (b, a) on the graph of 1−f , what is the corresponding point on the graph of

f ? Justify your answer.

x 1( )f x− 3 5 10 7 6

3 11 1

x f (x) 11

3 9 7

10 15 3




As you have seen in working through Item 7, if f is an invertible function f and a is the input for function f that gives b as output, then b is the input to the function 1−f that gives a as output. Conversely, if f is an invertible function f and b is the input to the function 1−f that gives a as output, then a is the input for function f that gives b as output. Stated more formally with function notation we have the following property: Inverse Function Property: For any invertible function f and any real numbers a and b in the domain and range of f, respectively,

( )f a b= if and only if ( )1f b a− = .

8. Explain why the Inverse Function Property holds, and express the idea in terms of points on the graphs of f and 1−f .

9. After Aisha had converted the temperatures in the scientific journal article from Kelvin to

Celsius, she decided, just for her own information, to calculate the corresponding Fahrenheit temperature for each Celsius temperature.

a. Use the formula ( )5 329

C F= − to find a formula for converting temperatures in the other

direction, from a temperature in degrees Celsius to the corresponding temperature in degrees Fahrenheit.

b. Now let ( )5( ) 329

g x x= − , as in Item 2, so that ( )g x is the temperature in degrees

Celsius corresponding to a temperature of x degrees Fahrenheit. Then 1g− is the function

that converts Celsius temperatures to Fahrenheit. Find a formula for 1( )−g x .

c. Check that, for the functions g and 1g− from part b, ( )1 ( )− =g g x x and ( )1( )− =g g x x

for any real number x.

Our next goal is to develop a general algebraic process for finding the formula for the inverse function when we are given the formula for the original function. This process focuses on the idea that we usually represent functions using x for inputs and y for outputs and applies the inverse function property. 10. We now find inverses for some of the currency conversion functions of Item 3.

a. Return to the function P from Item 3, part a, that converts Japanese yen to Mexican pesos. Rewrite the formula replacing ( )P x with y and then solve for x in terms of y.




b. The function 1−P converts Mexican pesos back to Japanese yen. By the inverse function

property, if ( )=y P x , then ( )1− =P y x . Use the formula for x, from part a, to write a

formula for ( )1−P y in terms of y.

c. Write a formula for ( )1−P x .

d. Find a formula for ( )1E x− , where E is the function that converts Mexican pesos to Euros

from Item 3, part b.

e. Find a formula for ( )1D x− , where D is the function that converts Euros to US dollars

from Item 3, part c.

11. Aisha plans to include several digital photos on her poster for the school-district science fair.

Her teacher gave her guidelines recommending an area of 2.25 square feet for photographs. Based on the size of her tri-fold poster, the area of photographs can be at most 2.5 ft high. Aisha thinks that the area should be at least 1.6 feet high to be in balance with the other items on the poster.

a. Aisha needs to decide on the dimensions for the area for photographs in order to complete her plans for poster layout. Define a function W such that W(x) gives the width, in feet, of the photographic area when the height is x feet.

b. Write a definition for the inverse function, 1W − .

In the remaining items you will explore the geometric interpretation of this relationship between points on the graph of a function and its inverse.

12. We start the exploration with the function W from Item 11.

a. Use technology to graph the functions W and 1W − on the same coordinate axes. Use a square viewing window.

b. State the domain and range of the function W.




c. State the domain and range of the function 1W − .

d. In general, what are the relationships between the domains and ranges of an invertible

function and its inverse? Explain your reasoning.

13. Explore the relationship between the graph of a function and the graph of its inverse function.

For each part below, use a standard, square graphing window with 10 10− ≤ ≤x and 10 10− ≤ ≤y .

a. For functions in Item 6, part a, graph f, 1f − , and the line y = x on the same axes. b. For functions in Item 6, part c, graph f, 1f − , and the line y = x on the same axes. c. For functions in Item 6, part d, graph f, 1f − , and the line y = x on the same axes.

d. If the graphs were drawn on paper and the paper were folded along the line y = x, what

would happen?

e. Do you think that you would get the same result for the graph of any function f and its

inverse when they are drawn on the same axes using the same scale on both axes? Explain your reasoning.

Consider the function 3( ) −=f x

x.

a. Find the inverse function algebraically.

b. Draw an accurate graph of the function f on graph paper and use the same scale on both

axes.

c. What happens when you fold the paper along the line y = x? Why does this happen?

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Part A: Determining the Relationship between Bending and Force 1. First, we want to determine how the amount of bending changes when different amounts of force are applied. How can you collect data with these variables? How will you measure these variables? 2. Once you have decided how to collect your data, you want to record the amount of bending that takes place for 8 different amounts of force. (Discuss with your groups how to vary your amounts of force to be able to see a change in the amount of bending. Here our “force” is the weight of the pennies.)

a. Make a table that lists the amount of force for the eight different amounts of force.

b. Draw a scatterplot of these values.

3. By the shape of the plotted points, does this function seem to be linear, quadratic, or neither?

a. Using the Linear Regression, Quadratic Regression, Cubic Regression, and Quartic Regression functions on your calculator, how can we determine which model fits the data the best? What does it for a model to “fit the data the best?”

b. Which model seems to fit the data most closely? How do you know?

c. Sketch this function over your scatterplot.

4. Write the equation for the model that best fits your data from your calculator. What type

of function is this?

a. Give the domain and range for this function.

b. Using this function, predict how much the cantilever will bend for

c. Using this function, predict how much the cantilever will bend if you had 100,000 pennies.

d. Does this value make sense? Imagine what the ruler would look like if it was bending this much.




e. Recall the domain and range you specified for this function in (g). Consider your answers in parts (i) and (j). Given the context of the problem. Does the context restrict your domain and/or range? (Hint: At what force do you think the cantilever will break? How much can the ruler bend before it breaks?)

5. Is this function increasing or decreasing? In the context, what does that mean?

Part B: Determining the Relationship between Bending and Cantilever Length 1. Now, measure and record the amount of bending that takes place for at least 8 different lengths of the cantilever. Again determine within your group which lengths you can use to be able to see a different in the amount of bending.

a. Make a table that lists the amount of force for the eight different amounts of force.

b. Draw a scatterplot of these values.

c. By the shape of the plotted points, does this function seem to be linear, quadratic, or neither?

2. Using the Linear Regression, Quadratic Regression, Cubic Regression, and Quartic Regression functions on your calculator, determine which model fits the data the best.Which model seems to fit the data most closely?

a. Sketch this function over your scatterplot. b. In what ways does this function fit your data? In what ways does it not?

3. Write the equation for the model that best fits your data from your calculator. What type

of function is this?

a. Give the domain and range for this function.

b. Using this function, predict how much the cantilever will bend for

c. Using this function, predict how much the cantilever will bend if the length of the cantilever was 50 inches.

d. Does this value make sense? Why or why not?




e. Recall the domain and range you specified for this function in (f). Consider your answers in parts (b), (g) and (h). Given this problem, how does the context restrict your domain and/or range?

4. Is this function increasing or decreasing? In the context, what does that mean?

5. What type of function is this?




Characteristics of Polynomial Functions Learning Task:

1. In the Cantilever Learning Task we learned about a third degree polynomial function, also called a cubic function. What do you think polynomial means? Let’s break down the word: poly- and –nomial. What does “poly” mean? a. A monomial is a numeral, variable, or the product of a numeral and one or more variables. For example: -1, ½, 3x, 2xy. Give a few examples of other monomials:

b. What is a constant? Give a few examples:

c. A coefficient is the numerical factor of a monomial or the ___________ in front of the variable in a monomial.

Give some examples of monomials and their coefficients.

d. The degree of a monomial is the sum of the exponents of its variables. has degree 4. Why?

What is the degree of the monomial 3? Why?

e. Do you know what a polynomial is now? A polynomial function is defined as a function, f(x)=

, where the coefficients are real numbers. The degree of a polynomial (n) is equal to the greatest exponent of its variable. The coefficient of the variable with the greatest exponent ( ) is called the leading coefficient. For example, f(x) = is a third degree polynomial with a leading coefficient of 4. 2. Previously, you have learned about linear functions, which are first degree polynomial

functions, y = , where is the slope of the line and is the intercept (Recall: y = mx + b; here m is replaced by and b is replaced by .) Also, you have learned about quadratic functions, which are 2nd degree polynomial functions, which can be expressed as y = .

a 0 x n + a1 x n −1 + a 2 x n − 2 + ... + a n − 2 x 2 + a n − 3 x 1 + a n

a0

4 x 3 − 5 x 2 + x − 8

a 0 x 1 + a1 a0 a1a0 a1

a 0 x 2 + a1 x 1 + a 2




In the Cantilever Learning Task you found that a cubic function modeled the data in one of the investigations. A cubic function is a third degree polynomial function. There are also fourth, fifth, sixth, etc. degree polynomial functions. a. To get an idea of what these functions look like, we can graph the first through fifth degree polynomials with leading coefficients of 1. For each polynomial function, make a table of 6 points and then plot them so that you can determine the shape of the graph. Choose points that are both positive and negative so that you can get a good idea of the shape of the graph. Also, include the x intercept as one of your points. For example, for the first order polynomial function: . You may have the following table and graph:

x y -3 -3 -1 -1 0 0 2 2 5 5

10 10




b. Compare these five graphs. By looking at the graphs, describe in your own words how is different from . Also, how is different from ?

c. Note any other observations you make when you compare these graphs. 3. In this unit, we are going to discover different characteristics of polynomial functions by looking at patterns in their behavior. Polynomials can be classified by the number of monomials, or terms, as well as by the degree of the polynomial. The degree of the polynomial is the same as the term with the highest degree. Complete the following chart. Make up your own expression for the last row.

Example Degree Name No. of terms Name 2

The characteristics of the polynomial functions that you have explored through the Cantilever Learning Task are some important characteristics in being able to describe and to sketch graphs of other polynomial functions. Some of these characteristics we have already examined with linear and quadratic functions, and others will be new. 4. In order to examine their characteristics in detail so that we can find the patterns that arise in the behavior of polynomial functions, we can study some examples of polynomial functions and their graphs. Here are 8 polynomial functions and their accompanying graphs that we will use to refer back to throughout the task. Handout of Graphs of Polynomial Functions : f(x) = 2 ; k(x) = 5 +4;

22 3x +3x−

4 23x x+53 4 2x x− +




g(x) = 2 l(x) = 5 +4)

h(x) = m(x) = 4 7 22 24 ;

j(x)= 2 3 n(x) = 4 6 15 36 ); Each of these equations can be re-expressed as a product of linear factors by factoring the equations, as shown above in the gray equations. a. List the x-intercepts of j(x) using the graph above. How are these intercepts related to the linear factors in gray? b. Why might it be useful to know the linear factors of a polynomial function?




c. Although we will not factor higher order polynomial functions in this unit, you have factored quadratic functions in GPS Algebra. For review, factor the following second degree polynomials, or quadratics.

a) 12 b) 5 6 c) 2 6 10

d. Using these factors, find the roots of these three equations. e. Sketch a graph of the three quadratic equations above without using your calculator and then use your calculator to check your graphs. f. Although you will not need to be able to find all of the roots of higher order polynomials until a later unit, using what you already know, you can factor some polynomial equations and find their roots in a similar way. Try this one: 2 . What are the roots of this fifth order polynomial function? g. How many roots are there? Why are there not five roots since this is a fifth degree polynomial? h. Check the roots by generating a graph of this equation using your calculator. i. For other polynomial functions, we will not be able to draw upon our knowledge of factoring quadratic functions to find zeroes. For example, you may not be able to factor 85 14 , but can you still find its zeros by graphing it in your calculator? How? Write are the zeros of this polynomial function.




5. Symmetry The first characteristic of these 8 polynomials functions we will consider is symmetry. a. Sketch a function you have seen before that has symmetry about the y-axis.

Describe in your own words what it means to have symmetry about the y-axis. What is do we call a function that has symmetry about the y-axis? b. Sketch a function you have seen before that has symmetry about the origin.

Describe in your own words what it means to have symmetry about the origin. What do we call a function that has symmetry about the origin?




c. Using the table below and your handout of the following eight polynomial functions, classify the functions by their symmetry.

Function

Symmetry about the y axis?

Symmetry about the origin?

Even, Odd, or Neither?

f(x) = 2 2 g(x) = 2 2 h(x) = 3 j(x)= 3 2 2 3 k(x) = 4 5 2+4

l(x) = 4 5 2+4)

m(x) = 125 4 4 7 3 22 2 24

n(x) = 12

5 4 4 7 3 22 2 24 )

d. Now, sketch your own higher order polynomial function (an equation is not needed) with symmetry about the y-axis. e. Now, sketch your own higher order polynomial function with symmetry about the origin. f. Using these examples from the handout and the graphs of the first through fifth degree polynomials you made, why do you think an odd function may be called an odd function? Why are even functions called even functions? g. Why don’t we talk about functions that have symmetry about the x-axis? Sketch a graph that has symmetry about the x-axis. What do you notice?

6. Domain and Range Another characteristic of functions that you have studied is domain and range. For each polynomial function, determine the domain and range.

Function

Domain Range

f(x) = 2 3 g(x) = 2 2 h(x) = 3 j(x) = 3 2 2 3 k(x) = 4 5 2+4

l(x) = 4 5 2+4)

m(x) = 125 4 4 7 3 22 2 24

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7. Zeroes

a. We can also describe the functions by determining some points on the functions. We can find the x-intercepts for each function as we discussed before. Under the column labeled “x-intercepts” write the ordered pairs (x, y) of each intercept and record the number of intercepts in the next column. Also record the degree of the polynomial.

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Degree X-intercepts Zeros Number of Zeros

f(x) = x2+ 2x g(x) = 2x2 + x h(x) = 3 j(x)= 3 2 2 3 k(x) = 4 5 2+4

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n(x) = 12

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b. These x-intercepts are called the zeros of the polynomial functions. Why do you think they have this name? c. Fill in the column labeled “Zeroes” by writing the zeroes that correspond to the x-intercepts of each polynomial function, and also record the number of zeroes each function has.

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d. Make a conjecture about the relationship of degree of the polynomial and number of zeroes.

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b. Write a conjecture about the end behavior, whether it rises or falls at the ends, of a

function of the form for each pair of conditions below. Then test your conjectures on some of the 8 polynomial functions graphed on your handout.

Condition a: When n is even and a > 0, Condition b: When n is even and a < 0, Condition c: When n is odd and a > 0, Condition d: When n is odd and a < 0,

c. Based on your conjectures in part (b), sketch a fourth

degree polynomial function with a negative leading coefficient.

d. Now sketch a fifth degree polynomial with a positive leading coefficient.

Note we can sketch the graph with the end behavior even though we cannot determine where and how the graph behaves otherwise without an equation or without the zeros.

e. If we are given the real zeros of a polynomial function, we can combine what we know about end behavior to make a rough sketch of the function. Sketch the graph of the following functions using what you know about end behavior and zeros:

a) 2 3

b) 1 5 7




9. Critical Points Other points of interest in sketching the graph of a polynomial function are the points where the graph begins or ends increasing or decreasing.

Recall what it means for a point of a function to be an absolute minimum or an absolute maximum.

a. Which of the twelve graphs from part 8(a) have an absolute maximum?

b. Which have an absolute minimum?

c. What do you notice about the degree of these functions?

d. Can you ever have an absolute maximum AND an absolute minimum in the same

function? If so, sketch a graph with both. If not, why not?

e. For each of the following graphs from the handout, locate the turning points and the related intervals of increase and decrease, as you have determined previously for linear and quadratic polynomial functions.

Then record which turning points are relative minimum (the lowest point on a given portion of the graph) and relative maximum (the highest point on a given portion of the graph) values.

Function Degree Turning

Points Intervals of

Increase Intervals of Decrease

Relative Minimum

Relative Maximum

f(x) h(x) k(x) n(x)

f. Make a conjecture about the relationship of the degree of the polynomial and the number

of turning points that the polynomial has. Recall that this is the maximum number of turning points a polynomial of this degree can have because these graphs are examples in which all zeros have a multiplicity of one. .

g. Sometimes points that are relative minimums or maximums are also absolute minimums

or absolute maximum. Are any of the relative extrema in your table also absolute extrema?




10. Putting it all Together Now that you have explored various characteristics of polynomial functions, you will be able to describe and sketch graphs of polynomial functions when you are given their equations. If I give you the function: f(x) = (x - 3)(x - 1)2 then what can you tell me about the graph of this function? Make a sketch of the graph of this function, describe its end behavior, and locate its critical point and zeroes.




Program Evaluation Learning Task

WEIGHT LOSS PROGRAM EVALUATION LEARNING TASK: An organization has established a 12-week weight-loss program that they claim their participants on average lose 24 pounds in those 12 weeks! Here is an advertisement for the program:

1. Evaluation Questions You are part of a team that has been asked to evaluate this program and offer information about the strengths and weaknesses of the program. Many times the role of a program evaluator is to display data in meaningful ways to explain it to those who are interested in the results of the evaluation. However, first program evaluators must know what kinds of data to collect in order to answer any questions they may have. In order to know what data to collect, program evaluators need to understand what questions they are trying to answer about the program. a. What questions might you want answered if you were considering whether or not to join this program? b. What are some questions you might want answered if you were the director of this program?

With our 12-week weight loss program, on average participants lose 24 pounds! Below are our topics for discussion and focus for the program meetings: Week 1: Healthy weight starts with a healthy diet. Week 3: Supplementing a healthy diet with regular exercise. Week 6: Sharing experiences with the group. Week 9: Motivational guest speaker. Week 12: Final weigh in and celebration! SIGN UP TODAY BY CALLING: 123-456-7890




c. Are there other evaluation questions to consider? d. There may be many questions considered by the program evaluation team, which may consist of many members. What types of data might you collect to answer each of these questions? 2. Data Your participation on the team is to analyze the following data set that was collected by a team of researchers. The researchers recorded the data from the weigh-ins that participants do at each meeting and chose a class of participants to follow-up on how well they maintained the weight loss after the program by also conducting weigh-ins at three week intervals for 9 weeks once the program was completed. The following table contains the data that was collected on the last class of 5 participants, and they have asked you to summarize and analyze the trends of the data. In order to protect the participants’ identities, your team has labeled the participants A through E. The data points in the column labeled Week 0 are the original weights of the participants at the very first meeting.

Participants/Week 0 3 6 9 12 15 18 21A 290 281 268 274 269 275 286 293B 305 294 279 285 270 276 287 299C 250 244 236 244 232 238 244 255D* 204 196 183 188 180 185 191 200E* 181 175 168 173 162 166 175 179

* Denotes a female participant. a. Which of your above evaluation questions do you think you may be able to answer with this

data? b. In what ways do you think it would be useful to represent the above data to examine the

nature of the weight loss for the program’s participants?




3. Individual Data a. How did you decide to display the individual data? Why? If you didn’t display the individual data, how would you do so? b. How is this data useful? What trends to do see in the data? Consider just participant B. c . During which intervals did Participant B lose weight? Given the context, why do you think Participant B lost weight during these intervals? (Refer to the schedule of the Weight Loss Program for some ideas.) d. During which intervals did Participant B gain weight? Given the context why do you think Participant B gained weight during these intervals? e. Without fitting a curve to this data and just by looking at the data, what type of function do you think would fit this data? Why would a linear function not model this data? Would a quadratic function appropriately model this data? f. If a polynomial function were to be fit to this data, what degree do you think that function would have? Would the leading coefficient be positive or negative? Why? Sketch in the polynomial function you would use to model this data over your existing graph or plot. Can you interpret data points outside of the Week 0 through Week 21 with this function? Why or why not?




g. Does makes sense to use the entire domain and range of this function to model this data? Why or why not? Given our data, what would the domain and range of the function be that could model this data? What would be a reasonable range for a similar function that models any adult participant’s weight? h. Given the context, about how much do you think Participant B will weigh 30 weeks after the start of the program? One year after the start of the program? Why do you think this? How do these thoughts support restricting the domain of the polynomial function as you did in part (g)? i. How much do you think Participant B may have weighed at Week 10? Why? Think about the context of the problem when you answer this question. j. Using set notation, state the intervals of increase and decrease of the function that you drew. What point is the absolute minimum within for the function you drew to model this data for Participant B? What does this point represent, given the context of the problem? What point on the scatterplot represents the most Participant B weighed in the time interval data was collected? What is another point that is a relative minimum for your function? Interpret this point in the context. What is one point that is a relative maximum for this function? Interpret this point in the context.

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Suppose you could model the average female weight by week by a polynomial function, f(x). How could you translate this function into a function m(x) that would roughly model the average male weight by week?

Represent this translation symbolically by expressing the function m(x) in terms of f(x). It may help to recall how you would translate the function g(x) = x or h(x) = , and then generalize this to this situation with a higher order polynomial function.

Let a(x) represent the function that would model the average weight by week for all participants. Express a(x) as a translation of f(x).

Express a(x) as a translation of m(x). Do either of these functions have any real zeros? How do you know? Interpret what a real zero would mean in this context. 5. Report Given these explorations of the weight program data, compile a report summarizing your findings for the individual, average, and/or net weight loss/data (or any other data you considered) and suggest some strengths and weaknesses of the program. Also include any other data that would have helped you make evaluations about the program that should be included the next time the program is evaluated.




THE SWIMMING DEBATE LEARNING TASK:

1. The Task Alexis, Loren and Roxy are trying to determine who the fastest swimmer is by timing each others’ swims from one end of the pool to the other. The pool is an Olympic size pool with a 50 meter length, 25 meter width, and 2 meter depth as indicated in the drawing below. Loren swims first; he swims from point S (the starting point will be the exact center of the side of the pool) to point L (the top of the corner of the pool) in 51.538 seconds. Then Roxy swims from point S to point R (the bottom corner of the pool) in 51.578 second. Finally, Alexis swims from point S to point A (the top center of the other side of the pool) in 50.039 seconds. When Alexis hears her time, she exclaims, “Yes, I win! I am the fastest swimmer.” Loren then figures, “Well, you may have had the quickest time, but I am the fastest swimmer because I swam farther than you and had a quicker time than Roxy. Roxy rebuts, “Well if that’s the case, I swam even farther than Loren did and had almost the exact same time, so maybe I’m the fastest swimmer.” Assuming all measurements were exact and the swimmers swam in a straight line from their starting to finishing points, your task is to help Loren, Alexis and Roxy determine whose rate was the fastest. Make a sketch of the problem situation. How can you determine the distance that each person swam? 2. Distance Recall before having found the distance in two-dimensional space, for example finding the distance that someone has run on a flat surface like a track. This type of problem only has two dimensions, which can be represented by the two dimensional Cartesian coordinate system with 2 axes, which are commonly labeled the x and y axis. a. How many pieces are there in the 2-D coordinate system? What are these “pieces” called?

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Now that you know how to plot points in three dimensional space, we are one step further to being able to calculate a distance in space, which is required by our problem we are trying to solve. Let’s return to the sketch a graph of our problem situation. Let the starting point, S, be the origin of the coordinate system. Describe the points L, A and R with an ordered triple by letting the x-coordinate be the length, the y-coordinate be the width and the z-coordinate be the depth. What are the three distances that the problem requires us to calculate? Write the line segments that represent these distances from your drawing. How will calculating these three distances be different from each other? Can you already find any of these distances with what you already know? If so, go ahead and calculate them now. In order to determine a 3-dimensional distance, we can review how we calculated distance in two dimensions and extend that idea to three dimensions. Recall how to calculate distance in two dimensions. Determine the distance from A (-3, -1) to B (2, 5). Using a graph, show how you know your answer is correct. Include the name of the Theorem that we use to show this. Now that we recall the derivation of the distance formula, we can extend that idea for three dimensions.

f. Write the equation for how you would find in the figure below. Write a similar equation for . Then, write an equation expressing e in terms of a, b, and d.

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The length of segment which is labeled b represents a length along the y-dimension, so we can express this length in terms of the y-coordinates of points N and M:

The length of segment which is labeled d now represents a length along the z-axis, so we can express this length in terms of the z-coordinates of points M and L:

The length of segment which is labeled e is the distance we are trying to find.

Now using this information, re-express = in terms of the coordinates of points O, L, M, and N:

We are now able to find the distance between two points, if we know their coordinates, by visualizing the two triangles and using the Pythagorean Theorem. Now, you can apply what you have learned about finding distance in a three dimensional space to help Loren, Alexis, and Roxy determine who swam at the fastest rate. Calculate the distance each swimmer swam. Show how the distance formula was used for each calculation. Write Roxy’s distance in terms of the coordinates of the points s, A, L, and R. Use this information to determine who swam the fastest. Record the distances, times, and rates in a table. Swimmer Distance (s) Time (s) Rate (m/s)

Alexis 50 m 48.10 1.040 Loren 51.539 48.28 1.068 Roxy 51.578 48.72 1.059

Who had the shortest time? Who had the fastest rate? Who swam the longest distance? Explain to Alexis, Loren, and Roxy who was the fastest swimmer and why.




Building a Swimming Pool Alexis wants to have a pool in her backyard so that she can practice swimming at her house. Even though she knows she doesn’t need one as big as an Olympic size swimming pool, she does want to have all of the dimensions proportional to the dimensions of an Olympic size swimming pool. 1. If the length of her pool is going to be x, what will be the width of her pool? 2. What will be the depth of her pool? 3. Express the volume Alexis’s pool with a length of x meters: Make a sketch of this function. 4. On what intervals is the function increasing? Decreasing? 5. How would you describe the end behavior of this function? Is this what you would expect given the degree and lead coefficient of this function? 6. What are the zeroes of this function? Give the multiplicity of each zero. 7. Explain in your own words how you determined the multiplicity of the zeroes you found. 8. If you build a pool that is 30 meters long, what is the volume of the pool? Plot this point on your graph and label it P. 9. If you build a pool that is 1.5 meters deep, what is the volume of the pool? Plot this point on your graph and label it Q. 10. Consider how shallow a pool can be and still be able to swim in it. What should the lower bound on the depth of the pool be? 11. Put a restriction on x, the length of the pool, due to this lower bound on the depth. What would the lower bound for the length be? Write this in terms of x. 12. What is the upper bound on the length? 13. Now, graph these two restrictions with your polynomial function for volume. What is your restricted domain and range?




14. Using this graph, determine one possible set of dimensions that the new pool may have.

15. Plot the point on the graph that corresponds to these dimensions. Call the point P and label the x and y values.

16. Shade the area that contains all possible values that x can be.

Alexis’s parents decided they would like the pool to hold less than 300,000 gallons of water. Add a constraint to your graph so that the volume equals 300,000 gallons of water. [1 cubic meter = 264.172 gallons].

17. What is the longest pool Alexis can have with this constraint? Plot this point on your

graph.

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