Math Problem Statement

Find (f ∘ g)(x), (g ∘ f)(x), and (f ∘ g)(2) for the following functions: 1) f(x) = 2x, g(x) = x + 5 2) f(x) = 4x, g(x) = x - 3 3) f(x) = 2x + 1, g(x) = 3x - 2

Solution

Let's work through the three problems provided in the image. The goal is to find:

  1. (fg)(x)(f \circ g)(x), which means f(g(x))f(g(x)),
  2. (gf)(x)(g \circ f)(x), which means g(f(x))g(f(x)), and
  3. (fg)(2)(f \circ g)(2), which means applying f(g(2))f(g(2)).

1. f(x)=2xf(x) = 2x, g(x)=x+5g(x) = x + 5

  • (fg)(x)(f \circ g)(x): This means f(g(x))=f(x+5)f(g(x)) = f(x + 5). f(x+5)=2(x+5)=2x+10f(x + 5) = 2(x + 5) = 2x + 10 So, (fg)(x)=2x+10(f \circ g)(x) = 2x + 10.

  • (gf)(x)(g \circ f)(x): This means g(f(x))=g(2x)g(f(x)) = g(2x). g(2x)=2x+5g(2x) = 2x + 5 So, (gf)(x)=2x+5(g \circ f)(x) = 2x + 5.

  • (fg)(2)(f \circ g)(2): First, find g(2)g(2), then apply ff. g(2)=2+5=7g(2) = 2 + 5 = 7 Now, find f(7)f(7): f(7)=2(7)=14f(7) = 2(7) = 14 So, (fg)(2)=14(f \circ g)(2) = 14.


2. f(x)=4xf(x) = 4x, g(x)=x3g(x) = x - 3

  • (fg)(x)(f \circ g)(x): This means f(g(x))=f(x3)f(g(x)) = f(x - 3). f(x3)=4(x3)=4x12f(x - 3) = 4(x - 3) = 4x - 12 So, (fg)(x)=4x12(f \circ g)(x) = 4x - 12.

  • (gf)(x)(g \circ f)(x): This means g(f(x))=g(4x)g(f(x)) = g(4x). g(4x)=4x3g(4x) = 4x - 3 So, (gf)(x)=4x3(g \circ f)(x) = 4x - 3.

  • (fg)(2)(f \circ g)(2): First, find g(2)g(2), then apply ff. g(2)=23=1g(2) = 2 - 3 = -1 Now, find f(1)f(-1): f(1)=4(1)=4f(-1) = 4(-1) = -4 So, (fg)(2)=4(f \circ g)(2) = -4.


3. f(x)=2x+1f(x) = 2x + 1, g(x)=3x2g(x) = 3x - 2

  • (fg)(x)(f \circ g)(x): This means f(g(x))=f(3x2)f(g(x)) = f(3x - 2). f(3x2)=2(3x2)+1=6x4+1=6x3f(3x - 2) = 2(3x - 2) + 1 = 6x - 4 + 1 = 6x - 3 So, (fg)(x)=6x3(f \circ g)(x) = 6x - 3.

  • (gf)(x)(g \circ f)(x): This means g(f(x))=g(2x+1)g(f(x)) = g(2x + 1). g(2x+1)=3(2x+1)2=6x+32=6x+1g(2x + 1) = 3(2x + 1) - 2 = 6x + 3 - 2 = 6x + 1 So, (gf)(x)=6x+1(g \circ f)(x) = 6x + 1.

  • (fg)(2)(f \circ g)(2): First, find g(2)g(2), then apply ff. g(2)=3(2)2=62=4g(2) = 3(2) - 2 = 6 - 2 = 4 Now, find f(4)f(4): f(4)=2(4)+1=8+1=9f(4) = 2(4) + 1 = 8 + 1 = 9 So, (fg)(2)=9(f \circ g)(2) = 9.


Let me know if you'd like more details or if you have any further questions!

Here are 5 questions that could expand your understanding:

  1. How do the compositions of functions differ when f(x)f(x) and g(x)g(x) are nonlinear?
  2. What happens to the composition if one of the functions is a constant?
  3. How would you approach finding (fg)(x)(f \circ g)(x) if f(x)f(x) and g(x)g(x) involve fractions?
  4. How can compositions of functions be applied in real-world scenarios?
  5. Can you derive the inverse of a composed function (fg)1(x)(f \circ g)^{-1}(x)?

Tip: When composing functions, always start from the innermost function and work outward step by step to avoid mistakes.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra

Formulas

(f ∘ g)(x) = f(g(x))
(g ∘ f)(x) = g(f(x))

Theorems

Function Composition Theorem

Suitable Grade Level

Grades 9-12