Math Problem Statement

Find the value of (f ∘ g)⁻¹(5) where f(x) = 3x + 3 and g(x) = 2 - 2x.

Solution

Let's solve the problem step by step:

We are given:

  • f(x)=3x+3f(x) = 3x + 3
  • g(x)=22xg(x) = 2 - 2x

We need to find the value of (fg)1(5)(f \circ g)^{-1}(5). Here's the step-by-step process:


Step 1: Compute fg(x)f \circ g(x)

This is the composition of f(x)f(x) and g(x)g(x): (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x)) Substitute g(x)=22xg(x) = 2 - 2x into f(x)f(x): f(g(x))=f(22x)f(g(x)) = f(2 - 2x) Substitute f(x)=3x+3f(x) = 3x + 3: f(22x)=3(22x)+3f(2 - 2x) = 3(2 - 2x) + 3 Simplify: f(22x)=66x+3=96xf(2 - 2x) = 6 - 6x + 3 = 9 - 6x Thus: (fg)(x)=96x(f \circ g)(x) = 9 - 6x


Step 2: Find the inverse of fg(x)f \circ g(x)

We need (fg)1(y)(f \circ g)^{-1}(y). Start by letting y=fg(x)y = f \circ g(x): y=96xy = 9 - 6x Solve for xx in terms of yy: y9=6xy - 9 = -6x x=9y6x = \frac{9 - y}{6} Thus: (fg)1(y)=9y6(f \circ g)^{-1}(y) = \frac{9 - y}{6}


Step 3: Compute (fg)1(5)(f \circ g)^{-1}(5)

Substitute y=5y = 5 into the inverse: (fg)1(5)=956(f \circ g)^{-1}(5) = \frac{9 - 5}{6} Simplify: (fg)1(5)=46=23(f \circ g)^{-1}(5) = \frac{4}{6} = \frac{2}{3}


Final Answer:

(fg)1(5)=23(f \circ g)^{-1}(5) = \frac{2}{3}


Do you want a detailed explanation of any step, or help with related problems? Here are five related questions you can explore:

  1. How do you find the inverse of a composite function in general?
  2. What is the domain of fg(x)f \circ g(x) for these specific functions?
  3. How would the solution change if f(x)f(x) or g(x)g(x) were nonlinear functions?
  4. Can you graph f(x)f(x), g(x)g(x), and fg(x)f \circ g(x) for better understanding?
  5. How does the derivative of fg(x)f \circ g(x) relate to the derivatives of f(x)f(x) and g(x)g(x)?

Tip: Always double-check the domain restrictions of functions when computing inverses

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Math Problem Analysis

Mathematical Concepts

Composition of Functions
Inverse Functions
Algebra

Formulas

f ∘ g(x) = f(g(x))
(f ∘ g)⁻¹(y) = (9 - y)/6

Theorems

Composition of Functions
Inverse Function Theorem

Suitable Grade Level

Grades 9-11