Math Problem Statement

Given functions f(x) = x + 3 and g(x) = 3x - 5, find the inverses f⁻¹(x) and g⁻¹(x). Also, determine the compositions (f⁻¹ ∘ g⁻¹)(x) and (g⁻¹ ∘ f⁻¹)(x).

Solution

Let's solve the problem step by step from the image.

Given Functions:

  • f(x)=x+3f(x) = x + 3
  • g(x)=3x5g(x) = 3x - 5

We are asked to determine the following:

  1. f1(x)f^{-1}(x) and g1(x)g^{-1}(x) (inverse functions).
  2. The composition (f1g1)(x)(f^{-1} \circ g^{-1})(x).
  3. The composition (g1f1)(x)(g^{-1} \circ f^{-1})(x).

Step 1: Finding the inverse of f(x)f(x)

The function is f(x)=x+3f(x) = x + 3. To find f1(x)f^{-1}(x):

  1. Set y=f(x)=x+3y = f(x) = x + 3.
  2. Solve for xx: y=x+3x=y3.y = x + 3 \quad \Rightarrow \quad x = y - 3. So, the inverse function is: f1(x)=x3.f^{-1}(x) = x - 3.

Step 2: Finding the inverse of g(x)g(x)

The function is g(x)=3x5g(x) = 3x - 5. To find g1(x)g^{-1}(x):

  1. Set y=g(x)=3x5y = g(x) = 3x - 5.
  2. Solve for xx: y=3x53x=y+5x=y+53.y = 3x - 5 \quad \Rightarrow \quad 3x = y + 5 \quad \Rightarrow \quad x = \frac{y + 5}{3}. So, the inverse function is: g1(x)=x+53.g^{-1}(x) = \frac{x + 5}{3}.

Step 3: Finding (f1g1)(x)(f^{-1} \circ g^{-1})(x)

This composition means applying g1(x)g^{-1}(x) first and then applying f1(x)f^{-1}(x) to the result. So: (f1g1)(x)=f1(g1(x))=f1(x+53).(f^{-1} \circ g^{-1})(x) = f^{-1}\left(g^{-1}(x)\right) = f^{-1}\left(\frac{x + 5}{3}\right). Now substitute f1(x)=x3f^{-1}(x) = x - 3: f1(x+53)=x+533.f^{-1}\left(\frac{x + 5}{3}\right) = \frac{x + 5}{3} - 3. Simplifying: x+533=x+5393=x43.\frac{x + 5}{3} - 3 = \frac{x + 5}{3} - \frac{9}{3} = \frac{x - 4}{3}. Thus: (f1g1)(x)=x43.(f^{-1} \circ g^{-1})(x) = \frac{x - 4}{3}.

Step 4: Finding (g1f1)(x)(g^{-1} \circ f^{-1})(x)

This composition means applying f1(x)f^{-1}(x) first and then applying g1(x)g^{-1}(x) to the result. So: (g1f1)(x)=g1(f1(x))=g1(x3).(g^{-1} \circ f^{-1})(x) = g^{-1}(f^{-1}(x)) = g^{-1}(x - 3). Now substitute g1(x)=x+53g^{-1}(x) = \frac{x + 5}{3}: g1(x3)=(x3)+53=x+23.g^{-1}(x - 3) = \frac{(x - 3) + 5}{3} = \frac{x + 2}{3}. Thus: (g1f1)(x)=x+23.(g^{-1} \circ f^{-1})(x) = \frac{x + 2}{3}.

Final Answers:

  • f1(x)=x3f^{-1}(x) = x - 3
  • g1(x)=x+53g^{-1}(x) = \frac{x + 5}{3}
  • (f1g1)(x)=x43(f^{-1} \circ g^{-1})(x) = \frac{x - 4}{3}
  • (g1f1)(x)=x+23(g^{-1} \circ f^{-1})(x) = \frac{x + 2}{3}

Would you like further details or have any questions?


Here are five related questions you can explore:

  1. How do we find the inverse of more complex functions?
  2. What is the graphical interpretation of inverse functions?
  3. Can every function have an inverse?
  4. How do you determine if a function is one-to-one and invertible?
  5. How do compositions of inverse functions behave in general?

Tip: Always ensure the function is one-to-one before finding its inverse, as only one-to-one functions have inverses.

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Math Problem Analysis

Mathematical Concepts

Algebra
Inverse Functions
Function Composition

Formulas

Inverse of a function f(x): Solve y = f(x) for x
Composition of functions: (f ∘ g)(x) = f(g(x))

Theorems

Inverse Function Theorem: If f is a one-to-one function, f⁻¹ exists.
Composition of Inverse Functions: (f⁻¹ ∘ f)(x) = x

Suitable Grade Level

Grade 10-12