Math Problem Statement

Find (f ∘ g)(x), (g ∘ f)(x), and (f ∘ g)(2) for the functions f(x) = 2x and g(x) = x + 5.

Solution

The problem asks for the composition of two functions ff and gg. The given functions are:

  • f(x)=2xf(x) = 2x
  • g(x)=x+5g(x) = x + 5

1. Finding (fg)(x)(f \circ g)(x), i.e., f(g(x))f(g(x)):

This means we substitute g(x)g(x) into f(x)f(x).

f(g(x))=f(x+5)=2(x+5)=2x+10f(g(x)) = f(x+5) = 2(x+5) = 2x + 10

Thus, (fg)(x)=2x+10(f \circ g)(x) = 2x + 10.

2. Finding (gf)(x)(g \circ f)(x), i.e., g(f(x))g(f(x)):

This means we substitute f(x)f(x) into g(x)g(x).

g(f(x))=g(2x)=2x+5g(f(x)) = g(2x) = 2x + 5

Thus, (gf)(x)=2x+5(g \circ f)(x) = 2x + 5.

3. Finding (fg)(2)(f \circ g)(2):

Here, we need to calculate (fg)(x)(f \circ g)(x) when x=2x = 2.

We already know that (fg)(x)=2x+10(f \circ g)(x) = 2x + 10.

(fg)(2)=2(2)+10=4+10=14(f \circ g)(2) = 2(2) + 10 = 4 + 10 = 14

Thus, (fg)(2)=14(f \circ g)(2) = 14.


Would you like further details or have any questions?
Here are 5 related questions to extend this topic:

  1. What is the general formula for the composition of functions?
  2. How do we find the inverse of a composed function fgf \circ g?
  3. Can we always reverse the order of composition, i.e., fg=gff \circ g = g \circ f?
  4. How do you determine the domain of a composed function?
  5. What are some real-world applications of function compositions?

Tip: When working with function compositions, always substitute one function fully into the other to avoid errors in simplification.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra

Formulas

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

Theorems

Function Composition

Suitable Grade Level

Grades 9-12