Math Problem Statement

Find f ∘ g and g ∘ f. f(x) = 3

x − 9 , g(x) = x3 + 1 (a)
f ∘ g

Solution

To find fgf \circ g, we need to evaluate f(g(x))f(g(x)), which means we substitute g(x)g(x) into f(x)f(x).

Given the functions:

  • f(x)=3x9f(x) = 3x - 9
  • g(x)=x3+1g(x) = x^3 + 1

Step 1: Substitute g(x)g(x) into f(x)f(x)

f(g(x))=3(g(x))9f(g(x)) = 3(g(x)) - 9 Since g(x)=x3+1g(x) = x^3 + 1, substitute this into f(g(x))f(g(x)): f(g(x))=3(x3+1)9f(g(x)) = 3(x^3 + 1) - 9

Step 2: Simplify the expression

f(g(x))=3x3+39f(g(x)) = 3x^3 + 3 - 9 f(g(x))=3x36f(g(x)) = 3x^3 - 6

Thus, fg=3x36f \circ g = 3x^3 - 6.

Would you like to proceed with gfg \circ f? Let me know if you want more details or have any questions.

Here are 5 questions related to the problem:

  1. What is the domain of the function fgf \circ g?
  2. How does the composition of functions affect their range?
  3. Can the order of composition fgf \circ g change the result compared to gfg \circ f?
  4. What happens if g(x)g(x) is a non-polynomial function?
  5. How do we interpret function composition graphically?

Tip: Always pay attention to the domain of both functions when performing compositions to avoid undefined values!

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Math Problem Analysis

Mathematical Concepts

Algebra
Function Composition

Formulas

f(g(x)) = f(x^3 + 1) = 3(x^3 + 1) - 9
g(f(x)) = g(3x - 9)

Theorems

Function Composition

Suitable Grade Level

Grades 10-12