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Ch. 2 - Functions and Graphs
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 3, Problem 77a

Express the given function h as a composition of two functions ƒ and g so that h(x) = (fog) (x). h(x) = ∛(x² – 9)

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Step 1: Understand the problem. The goal is to express the given function h(x) = ∛(x² – 9) as a composition of two functions ƒ(x) and g(x) such that h(x) = (ƒ ∘ g)(x), which means h(x) = ƒ(g(x)).
Step 2: Identify the inner function g(x). Look at the expression inside the cube root, x² – 9. This suggests that g(x) = x² – 9.
Step 3: Identify the outer function ƒ(x). The outer function operates on the result of g(x). Since h(x) = ∛(x² – 9), the cube root operation applies to g(x). Therefore, ƒ(x) = ∛x or equivalently ƒ(x) = x^(1/3).
Step 4: Verify the composition. Substitute g(x) into ƒ(g(x)) to ensure it matches h(x). ƒ(g(x)) = ƒ(x² – 9) = ∛(x² – 9), which is the original h(x).
Step 5: Conclude that the functions are ƒ(x) = x^(1/3) and g(x) = x² – 9, and their composition satisfies h(x) = (ƒ ∘ g)(x).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Function Composition

Function composition involves combining two functions, where the output of one function becomes the input of another. In this context, if h(x) = (f o g)(x), it means h(x) can be expressed as f(g(x)). Understanding how to break down a function into simpler components is essential for solving the problem.
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Cube Root Function

The cube root function, denoted as ∛x, is the inverse of the cubic function x³. It is important to recognize how this function behaves, particularly its domain and range, as well as how it can be manipulated algebraically. In the given function h(x) = ∛(x² - 9), understanding the cube root will help in identifying suitable functions f and g.
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Quadratic Functions

Quadratic functions are polynomial functions of the form ax² + bx + c, where a, b, and c are constants. In the expression x² - 9, we see a difference of squares, which can be factored. Recognizing the structure of quadratic expressions is crucial for determining how to express h(x) as a composition of two simpler functions.
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