Math Problem Statement

For each pair of functions f and g below, find f(g(x)) and g(f(x)). Then, determine whether f and g are inverses of each other.

Solution

Let's go over each part of the problem in the image.

Problem (a)

The functions are:

  • f(x)=4xf(x) = -\frac{4}{x}, where x0x \neq 0
  • g(x)=4xg(x) = -\frac{4}{x}, where x0x \neq 0

You are asked to find f(g(x))f(g(x)) and g(f(x))g(f(x)), and determine whether ff and gg are inverses.

Step 1: Find f(g(x))f(g(x))

Substitute g(x)g(x) into f(x)f(x): f(g(x))=f(4x)=4(4x)=xf(g(x)) = f\left(-\frac{4}{x}\right) = -\frac{4}{\left(-\frac{4}{x}\right)} = x

Step 2: Find g(f(x))g(f(x))

Substitute f(x)f(x) into g(x)g(x): g(f(x))=g(4x)=4(4x)=xg(f(x)) = g\left(-\frac{4}{x}\right) = -\frac{4}{\left(-\frac{4}{x}\right)} = x

Since both f(g(x))=xf(g(x)) = x and g(f(x))=xg(f(x)) = x, the functions ff and gg are inverses of each other.

Problem (b)

The functions are:

  • f(x)=x+3f(x) = -x + 3
  • g(x)=x+3g(x) = x + 3

Step 1: Find f(g(x))f(g(x))

Substitute g(x)g(x) into f(x)f(x): f(g(x))=f(x+3)=(x+3)+3=x3+3=xf(g(x)) = f(x + 3) = -(x + 3) + 3 = -x - 3 + 3 = -x

Step 2: Find g(f(x))g(f(x))

Substitute f(x)f(x) into g(x)g(x): g(f(x))=g(x+3)=(x+3)+3=x+6g(f(x)) = g(-x + 3) = (-x + 3) + 3 = -x + 6

Since f(g(x))=xf(g(x)) = -x and g(f(x))=x+6g(f(x)) = -x + 6, the functions are not inverses of each other.


Would you like further details on any part of this? Here are 5 related questions to explore further:

  1. How do you determine if two functions are inverses using their compositions?
  2. What is the domain restriction for inverse functions, and why is it important?
  3. Can a function have more than one inverse?
  4. How does the algebraic process of simplifying compositions reveal inverse relationships?
  5. What are common pitfalls in determining if two functions are inverses?

Tip: Inverse functions always "undo" each other, meaning their compositions f(g(x))f(g(x)) and g(f(x))g(f(x)) must equal xx.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Inverse Functions
Algebra

Formulas

f(g(x)) = f(g(x))
g(f(x)) = g(f(x))
Two functions f and g are inverses if f(g(x)) = x and g(f(x)) = x

Theorems

Inverse Function Theorem
Compositions of Functions

Suitable Grade Level

Grades 10-12