Math Problem Statement

Given the definitions of f(x) and g(x) below, find the value of (g ∘ f)(-2). f(x) = 2x^2 + 4x + 2, g(x) = 2x - 7.

Solution

To solve the problem of finding (gf)(2)(g \circ f)(-2), let's break down the steps:

Step-by-Step Solution

  1. Understand the Composition of Functions: (gf)(x)(g \circ f)(x) means we first apply f(x)f(x) and then apply gg to the result of f(x)f(x). So, we need to find f(2)f(-2) first and then plug that result into gg.

  2. Find f(2)f(-2): Given: f(x)=2x2+4x+2f(x) = 2x^2 + 4x + 2 Substitute x=2x = -2: f(2)=2(2)2+4(2)+2f(-2) = 2(-2)^2 + 4(-2) + 2 Calculating each term:

    • (2)2=4(-2)^2 = 4, so 24=82 \cdot 4 = 8
    • 4(2)=84(-2) = -8
    • Adding these results: 88+2=28 - 8 + 2 = 2

    So, f(2)=2f(-2) = 2.

  3. Apply gg to f(2)f(-2): Now we use g(x)=2x7g(x) = 2x - 7 and substitute x=f(2)=2x = f(-2) = 2: g(2)=2(2)7=47=3g(2) = 2(2) - 7 = 4 - 7 = -3

Final Answer:

(gf)(2)=3(g \circ f)(-2) = -3

Would you like further details on function compositions, or do you have any additional questions?


Here are five related questions to expand your understanding:

  1. How do you compose functions with different types of expressions, such as trigonometric or exponential functions?
  2. What is the result of (fg)(2)(f \circ g)(-2) using the same functions given here?
  3. How can you determine the domain of a composed function?
  4. What happens to the range of f(x)f(x) when you compose it with g(x)g(x)?
  5. How do you apply the chain rule to compositions of functions in calculus?

Tip: When composing functions, always evaluate the inner function first and then apply the outer function to the result.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra

Formulas

Function composition: (g ∘ f)(x) = g(f(x))
Quadratic function: f(x) = 2x^2 + 4x + 2
Linear function: g(x) = 2x - 7

Theorems

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Suitable Grade Level

Grades 10-11