common core algebra 2
TRANSCRIPT
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Common Core Algebra 2
Chapter 5: Rational Exponents &
Radical Functions
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Chapter Summary
โข This first part of this chapter introduces radicals and ๐th roots and how these may be written as
rational exponents. A connection is made to the properties of exponents studied in Algebra I, noting
that now exponents can be rational numbers and are no longer restricted to being nonzero integers.
โข In the middle portion of this chapter, radical expressions, also written in rational exponent form, are
presented as functions and are graphed. This leads to a look at what the domains are for each function
type.
โข The graphs of radical functions are used to help students think about solutions of radical equations and
inequalities. Certainly, one goal is for students to recognize that solving radical equations is an
extension of solving other types of functions. The difference, however, is that sometimes extraneous
solutions are introduced when solving radical equations, so it is necessary to check apparent solutions.
โข The last lessons in the chapter involve performing the four basic operations on function and doing so
from multiple approaches: symbolic, numerical, and graphical. The last lesson introduces inverse
functionsโfinding the inverse of linear, simple polynomial, and radical functions, and noting that the
graphs of inverse functions are reflections in the line ๐ฆ = ๐ฅ.
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Section 5.1 โ ๐th Roots and Rational Exponents
Essential Question: How can you use a rational exponent to represent a power involving a radical?
What You Will Learn โข Find ๐th roots of numbers.
โข Evaluate expressions with rational exponents.
โข Solve equations using ๐th roots.
----------------------------------------------------------------------------------------------------------------------------- -----------------------------------
Previously, you learned that the ๐th root of ๐ can be represented as:
โ๐๐ = _______
for any real number ๐ any integer ๐ greater than 1.
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- EXPLORATION 1: Exploring the Definition of a Rational Exponent
Use a calculator to show that each statement is true.
(a) โ9 = 91/2 (b) โ2 = 21/2 (c) โ83
= 81/3 (d) โ124
= 121/4
----------------------------------------------------------------------------------------------------------------------------- -----------------------------------
EXPLORATION 2: Writing Expressions in Rational Exponent Form
Use the definition of a rational exponent and the properties of exponents to write each expression as a base with a
single rational exponent. Then use a calculator to evaluate each expression. Round your answers to two decimal places.
Example: (โ43
)2
= (41/3)2
= 42/3
โ 2.52
(a) (โ5)3
(b) (โ44
)2
(c) (โ93
)2
(d) โ923 (e) (โ10
5)
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_____________________
_____________________
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EXPLORATION 3: Writing Expressions in Radical Form
Use the properties of exponents and the definition of a rational exponent to write each expression as a radical raised to
an exponent. Then use a calculator to evaluate each expression. Round your answer to two decimal places.
Example: 52/3 = (51/3)2
= (โ53
)2
โ 2.92
(a) 82/3 (b) 65/2 (c) 123/4 (d) 103/2
----------------------------------------------------------------------------------------------------------------------------- -----------------------------------
COMMUNICATE YOUR ANSWER
How can you use a rational exponent to represent a power involving a radical?
Example 1: Evaluate each expression without using a calculator. Make sure you can explain your reasoning.
(a) 43/2 (b) 324/5 (c) 812/4 (d) 493/2 (e) 1006/3
**In general, for an integer ๐ greater than 1, if ๐๐ = ๐, then if we solve this equation for ๐, _______________________
we can say that ____________________________________________________________________________________.
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Rational Exponents
A rational exponent does not have to be of the form 1
๐ . Other rational numbers, such as
3
2 and โ
1
2, can also be used as
exponents. Two properties of rational exponents are shown below.
Example 2: Evaluate each expression using the above property.
(a) (โ64)2/3 (b) 32โ3/5 (c) (โ225)โ1/2
Solving Equations Using ๐th Roots
To solve an equation of the form ๐ข๐ = ๐, where ๐ข is an algebraic expression, take the ๐th root of each side.
Example 3: Find the real solution(s) of each of the following equations.
(a) 4๐ฅ5 = 128 (b) 1
2๐ฅ5 = 512 (c) (๐ฅ โ 3)4 = 21
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Section 5.2 โ Properties of Rational Exponents and Radicals
Essential Question: How can you use properties of exponents to simplify products and quotients of radicals?
What You Will Learn โข Use properties of rational exponents to simplify expressions with rational exponents.
โข Use properties of radical to simplify and write radical expressions in simplest form. -------------------------------------------------------------------------------------------------------------------------------------------------- -------------- EXPLORATION 1: Let ๐ and ๐ be real numbers. Use the properties of exponents to complete each statement. Then match each completed statement with the property it illustrates.
Statement Property
(a) ๐โ2 = ______, ๐ โ 0 A. Product of Powers (b) (๐๐)4 = ________ B. Power of a Power (c) (๐3)4 = ________ C. Power of a Product (d) ๐3 โข ๐4 = ________ D. Negative Exponent
(e) (๐
๐)
3= _______, ๐ โ 0 E. Zero Exponent
(f) ๐6
๐2 = _______, ๐ โ 0 F. Quotient of Powers
(g) ๐0 = _______, ๐ โ 0 G. Power of a Quotient
---------------------------------------------------------------------------------------------------------------------------------------------- ------------------ PROPERTIES OF RATIONAL EXPONENTS
The properties of integer exponents can also be applied to rational exponents.
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Example 1: Apply the properties of integer exponents to rational exponents by simplifying each expression. Use a calculator to check your answers.
(a) 52/3 โข 54/3 (b) (101/2)4 (c)
85/2
81/2
(d) 3
31/4 (e) (51/3 โข 72/3)3 (f) (
201/2
51/2 )3
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- SIMPLIFYING RADICAL EXPRESSIONS
The Power of a Product and Power of a Quotient properties can be expression using radical notation when ๐ =1
๐ for
some integer ๐ greater than 1.
Example 2: Use the properties of radicals to simplify each expression.
(a) โ123
โข โ183
(b) โ804
โ54 (c) โ135
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(d) โ2884
(e) โ645
(f) โ3,000,0006
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SIMPLIFYING VARIABLE EXPRESSIONS The properties of rational exponents and radicals can also be applied to expressions involving variables. Because a variable can be positive, negative, or zero, sometimes absolute value is needed when simplifying a variable expression.
**Absolute value is not needed when all variables are assumed to be positive.** ----------------------------------------------------------------------------------------------------------------------------------------------------------------
Letโs prove this by graphing the function ๐ฆ = โ๐ฅ๐๐ for values of ๐ that are even and odd.
ODD values of ๐ vs EVEN values of ๐
๐ฆ = โ๐ฅ33 ๐๐๐ ๐ฆ = โ๐ฅ55
๐ฆ = โ๐ฅ2 ๐๐๐ ๐ฆ = โ๐ฅ44
simplifies to _____________________ simplifies to ______________________
Example 3: Simplify the following expressions.
(a) โ๐ฅ3 (b) โ๐ฅ4 (c) โ๐ฅ5 (d) โ๐ฅ6 (e) โ๐ฅ7
(f) โ64๐ฅ2๐ฆ (g) โ80๐ฅ4๐ฆ2 (h) โ27๐ฆ63 (i) โ
๐ฅ4
๐ฆ8
4 (j) โ4๐8๐14๐55
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Section 5.3 โ Graphing Radical Functions
Essential Question: How can you identify the domain and range of a radical function?
What You Will Learn โข Graph radical functions.
โข Write transformations of radical functions.
โข Graph parabolas and circles. ------------------------------------------------------------------------------------------------------------------------------------------------ ---------------- MOTIVATION
Have you ever been in a car that skidded on a road surface or have ever seen skid marks on a road? By measuring the skid marks of a vehicle and taking into account information about the efficiency of the brakes and the
surface on which the car was traveling, a police officer can use a formula involving a square root function to estimate
how fast a car was traveling at the time of an accident.
The function is ๐ = โ30๐ท โข ๐ โข ๐, where ๐ is the speed in miles per hour, ๐ท is the skid distance in decimal feet, ๐ is the
drag factor for the road surface, and ๐ is the percent braking efficiency written as a decimal.
Evaluate the speed of a car if ๐ท = 120 feet, ๐ = 0.75 (for asphalt), and ๐ = 100% (all four wheels braking).
----------------------------------------------------------------------------------------------------------------------------- -----------------------------------
EXPLORATION 1: Identifying Graphs of Radical Functions
Match each function with its graph. Explain your reasoning. Then identify the domain and range of each function.
Functions Graphs
(a) ๐(๐ฅ) = โ๐ฅ
(b) ๐(๐ฅ) = โ๐ฅ3
(c) ๐(๐ฅ) = โ๐ฅ4
(d) ๐(๐ฅ) = โ๐ฅ5
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EXPLORATION 2: Identifying Graphs of Transformations
Match each transformation of ๐(๐ฅ) = โ๐ฅ with its graph. Explain your reasoning. Then identify the domain and range of
each function.
Functions Graphs
(a) ๐(๐ฅ) = โ๐ฅ + 2
(b) ๐(๐ฅ) = โ๐ฅ โ 2
(c) ๐(๐ฅ) = โ๐ฅ + 2 โ 2
(d) ๐(๐ฅ) = โโ๐ฅ + 2
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- Communicate Your Answer
How can you identify the domain and range of a radical function?
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Graphing Radical Functions
A radical function contains a radical expression with the independent variable in the radicand. When the radical is a
square root, the function is called a square root function. When the radical is a cube root, the function is called a cube
root function.
Example 1: Graph each function. Identify the domain and range of each function.
(a) ๐(๐ฅ) = โ1
4๐ฅ (b) ๐(๐ฅ) = โ3โ๐ฅ3
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Transforming Radical Functions
Example 2: Describe the transformation of ๐ represented by ๐. Write the equation of ๐. Then sketch the graph of
๐ and identify the domain and range of each function.
(a) ๐(๐ฅ) = โ๐ฅ ; ๐(๐ฅ) = ๐(๐ฅ โ 3) + 4 (b) ๐(๐ฅ) = โ๐ฅ3 ; ๐(๐ฅ) = 8๐(โ๐ฅ)
Example 3: Let the graph of ๐ be a horizontal shrink by a factor of 1
6 followed by a translation 3 units to the left of the
graph of ๐(๐ฅ) = โ๐ฅ3 . Write a rule for ๐.
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Section 5.4 โ Solving Radical Equations and Inequalities
Essential Question: How can you solve a radical equation?
What You Will Learn โข Solve equations containing radicals and rational exponents.
โข Solve radical inequalities
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- EXPLORATION 1: Solving Radical Equations
Match each radical equation with the graph of its related radical function. Explain your reasoning. Then use the graph
to solve the equation, if possible. Check your solutions.
Equation Graph # Solution
(a) โ๐ฅ โ 1 โ 1 = 0 ____________ ________________________________
(b) โ2๐ฅ + 2 โ โ๐ฅ + 4 = 0 ____________ ________________________________
(c) โ9 โ ๐ฅ2 = 0 ____________ ________________________________
(d) โ๐ฅ + 2 โ ๐ฅ = 0 ____________ ________________________________
(e) โโ๐ฅ + 2 โ ๐ฅ = 0 ____________ ________________________________
(f) โ3๐ฅ2 + 1 = 0 ____________ ________________________________
1. 2. 3.
4. 5. 6.
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Communicate Your Answer
How can you solve a radical equation?
Would you prefer to use a graphical or algebraic approach to solve the given equation? Explain your reasoning. Then
solve the equation.
โ๐ฅ + 3 โ โ๐ฅ โ 2 = 1
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- Solving Equations Equations with radicals that have variables in their radicands are called radical equations. An example of a radical
equation is 2โ๐ฅ + 1 = 4.
Example 1: Solving Radical Equations.
(a) Solve 2โ๐ฅ + 1 = 4 (b) โ2๐ฅ โ 93
โ 1 = 2
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Example 2: Solving a Real-Life Problem
In a hurricane, the mean sustained wind velocity ๐ฃ (in meters per second) can be modeled by ๐ฃ(๐) = 6.3โ1013 โ ๐,
where ๐ is the air pressure (in millibars) at the center of the hurricane. Estimate the air pressure at the center of the
hurricane when the mean sustained wind velocity is 54.5 meters per second.
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- Solving an Equation with an Extraneous Solution
Raising each side of an equation to the same exponent may introduce solutions that are not solutions of the original
equation. These solutions are called _____________________________________________ solutions. When you use
this procedure you should always check each apparent solution in the original equation.
Example 3: Solve the following radical equations.
(a) ๐ฅ + 1 = โ7๐ฅ + 15 (b) โ๐ฅ + 2 + 1 = โ3 โ ๐ฅ
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Solving an Equation with a Rational Exponent
When an equation contains a power with a rational exponent, you can solve the equation using a procedure similar to
the one for solving radical equations. In this case, you first isolate the power and then raise each side of the equation to
the reciprocal of the rational exponent.
Example 5: Solve the following equations.
(a) (2๐ฅ)3/4 + 2 = 10 (b) (๐ฅ + 30)1/2 = ๐ฅ
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- Solving Radical Inequalities For the purpose of this class, we will solve radical inequalities using a graphical approach ONLY. Example 6: Solve the following radical inequalities.
(a) 3โ๐ฅ โ 1 โค 12 (b) 4โ๐ฅ + 13
> 8
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Section 5.5 โ Performing Function Operations Essential Question: How can you arithmetically combine the equations of two functions? What You Will Learn
โข Add, subtract, multiply and divide functions. ----------------------------------------------------------------------------------------------------------------------------------------------------------------
Example 1: Adding Two Functions
Let ๐(๐ฅ) = 3โ๐ฅ and ๐(๐ฅ) = โ10โ๐ฅ. Find (๐ + ๐)(๐ฅ) and state the domain. Then evaluate the sum when ๐ฅ = 4.
Example 2: Subtracting Two Functions
Let ๐(๐ฅ) = 3๐ฅ3 โ 2๐ฅ2 + 5 and ๐(๐ฅ) = ๐ฅ3 โ 3๐ฅ2 + 4๐ฅ โ 2. Find (๐ โ ๐)(๐ฅ) and state the domain. Then evaluate the
difference when ๐ฅ = โ2.
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Example 3: Multiplying Two Functions
Let ๐(๐ฅ) = ๐ฅ2 and ๐(๐ฅ) = โ๐ฅ. Find (๐๐)(๐ฅ) and state the domain. Then evaluate the product when ๐ฅ = 9.
Example 4: Dividing Two Functions
Let ๐(๐ฅ) = 6๐ฅ and ๐(๐ฅ) = ๐ฅ3/4. Find (๐
๐) (๐ฅ) and state the domain. Then evaluate the quotient when ๐ฅ = 16.
Example 5: Performing Operations Using Technology
Let ๐(๐ฅ) = โ๐ฅ and ๐(๐ฅ) = โ9 โ ๐ฅ2. Use a graphing calculator to evaluate (๐ + ๐)(๐ฅ), (๐ โ ๐)(๐ฅ), (๐๐)(๐ฅ), and
(๐
๐) (๐ฅ) when ๐ฅ = 2. Round your answers to two decimal places.
Example 6: Solving a Real-Life Problem
For a white rhino, heart rate ๐ (in beats per minute) and life span ๐ (in minutes) are related to body mass ๐ (in
kilograms) by the functions: ๐(๐) = 241๐โ0.25 and ๐ (๐) = (6 ร 106)๐0.2.
(a) Find (๐๐ )(๐).
(b) Explain what (๐๐ )(๐) represents.
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Section 5.6 โ Inverse of a Function
Essential Question: How can you sketch the graph of the inverse of a function?
What You Will Learn โข Explore inverses of functions. โข Find and verify inverses of nonlinear functions. โข Solve real-life problems using inverse functions.
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- EXPLORATION 1: Graphing Functions and Their Inverses Each pair of functions are inverses of each other. Match each pair of equations with their corresponding graph. What do you notice about the graphs? Inverse Pairs Graphs (a) ๐(๐ฅ) = 4๐ฅ + 3
๐(๐ฅ) =๐ฅ โ 3
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(b) ๐(๐ฅ) = ๐ฅ3 + 1
๐(๐ฅ) = โ๐ฅ โ 13
(c) ๐(๐ฅ) = โ๐ฅ โ 3
๐(๐ฅ) = ๐ฅ2 + 3, ๐ฅ โฅ 0
(d) ๐(๐ฅ) =4๐ฅ + 4
๐ฅ + 5
๐(๐ฅ) =4 โ 5๐ฅ
๐ฅ โ 4
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EXPLORATION 2: Sketching Graphs of Inverse Functions
Use the graph of ๐ to sketch the graph of ๐, the inverse function of ๐, on the same set of coordinate axes. Explain your
reasoning.
(a) (b)
(c) (d)
Communicate Your Answer
How can you sketch the graph of the inverse of a function?
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Exploring Inverses of Functions
Functions that undo each other are called inverse functions. The graph of an inverse function is a reflection of the graph
of the original function. The line of reflection is _______________.
Because inverse functions interchange the input and output values of the original function, the domain and range are
also interchanged.
To find the inverse of a function algebraically, switch the roles of ๐ฅ and ๐ฆ, and then solve for ๐ฆ.
----------------------------------------------------------------------------------------------------------------------------- ----------------------------------- Example 1: Find the inverse of each of the following functions.
(a) ๐(๐ฅ) = 2๐ฅ + 3 Original Function: ๐(๐ฅ) = 2๐ฅ + 3
Inverse Function:
Graph of ๐ and its inverse:
(b) ๐(๐ฅ) = โ๐ฅ + 1 (c) ๐(๐ฅ) =1
4๐ฅ โ 2
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Inverses of Nonlinear Functions
In the previous examples, the inverses of the linear functions were also functions. However, inverses are not always
functions. The graphs of ๐(๐ฅ) = ๐ฅ2 and ๐(๐ฅ) = ๐ฅ3 are shown along with their reflections in the line ๐ฆ = ๐ฅ.
When the domain of ๐(๐ฅ) = ๐ฅ2 is _____________________________ to only nonnegative real numbers, the inverse of
๐ is a function.
Therefore the inverse of ๐(๐ฅ) = ๐ฅ2, ๐ฅ โฅ 0 is __________________.
------------------------------------------------------------------------------------------ ----------------------------------------------------------------------
You can use the graph of a function ๐ to determine whether the inverse of ๐ is a function by applying the
โ๐๐๐๐ง๐๐๐ก๐๐ ๐๐๐๐ ๐ก๐๐ ๐ก.
Example 2: Determine whether the inverse of ๐ is a function.
(a) ๐(๐ฅ) = ๐ฅ3 โ 1 (b) ๐(๐ฅ) = โ๐ฅ + 4 (c) ๐(๐ฅ) = ๐ฅ4 + 2 (d) ๐(๐ฅ) = 2โ๐ฅ โ 53
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Verifying Functions Are Inverses
Let ๐ and ๐โ1 be inverse functions. If ๐(๐) = ๐, then ๐โ1( ) = ______. So in general,
๐(๐โ1( )) = _____ and ๐โ1(๐( )) = _____
Example 3: Verify that ๐(๐ฅ) = 3๐ฅ โ 1 and ๐โ1(๐ฅ) =๐ฅ + 1
3 are inverse functions.
Example 4: Determine whether the functions are inverses.
(a) ๐(๐ฅ) = ๐ฅ + 5; ๐(๐ฅ) = ๐ฅ โ 5 (b) ๐(๐ฅ) = 8๐ฅ3; ๐(๐ฅ) = โ2๐ฅ3
(c) ๐(๐ฅ) = โ๐ฅ + 9
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5 ; ๐(๐ฅ) = 5๐ฅ5 โ 9 (d) ๐(๐ฅ) = 7๐ฅ3/2 โ 4; ๐(๐ฅ) = (
๐ฅ + 4
7)
3/2