Math Problem Statement

f(x) = 4x + 7 and g(x) = x^8; f(x) = sqrt(x^2 + 7) and g(x) = x^2 + 2. Find f ∘ g and g ∘ f for both cases.

Solution

Let's break down the two problems from the image involving function compositions fgf \circ g and gfg \circ f.

Problem 1:

Given: f(x)=4x+7andg(x)=x8f(x) = 4x + 7 \quad \text{and} \quad g(x) = x^8

  1. fgf \circ g (which means f(g(x))f(g(x))):

    • First, substitute g(x)=x8g(x) = x^8 into f(x)=4x+7f(x) = 4x + 7.
    • f(g(x))=f(x8)=4(x8)+7=4x8+7f(g(x)) = f(x^8) = 4(x^8) + 7 = 4x^8 + 7.
  2. gfg \circ f (which means g(f(x))g(f(x))):

    • Now, substitute f(x)=4x+7f(x) = 4x + 7 into g(x)=x8g(x) = x^8.
    • g(f(x))=g(4x+7)=(4x+7)8g(f(x)) = g(4x + 7) = (4x + 7)^8.

Problem 2:

Given: f(x)=x2+7andg(x)=x2+2f(x) = \sqrt{x^2 + 7} \quad \text{and} \quad g(x) = x^2 + 2

  1. fgf \circ g (which means f(g(x))f(g(x))):

    • Substitute g(x)=x2+2g(x) = x^2 + 2 into f(x)=x2+7f(x) = \sqrt{x^2 + 7}.
    • f(g(x))=f(x2+2)=(x2+2)2+7=x4+4x2+4+7=x4+4x2+11f(g(x)) = f(x^2 + 2) = \sqrt{(x^2 + 2)^2 + 7} = \sqrt{x^4 + 4x^2 + 4 + 7} = \sqrt{x^4 + 4x^2 + 11}.
  2. gfg \circ f (which means g(f(x))g(f(x))):

    • Substitute f(x)=x2+7f(x) = \sqrt{x^2 + 7} into g(x)=x2+2g(x) = x^2 + 2.
    • g(f(x))=g(x2+7)=(x2+7)2+2=x2+7+2=x2+9g(f(x)) = g(\sqrt{x^2 + 7}) = (\sqrt{x^2 + 7})^2 + 2 = x^2 + 7 + 2 = x^2 + 9.

Summary of Solutions:

  • For Problem 1:

    • fg=4x8+7f \circ g = 4x^8 + 7
    • gf=(4x+7)8g \circ f = (4x + 7)^8
  • For Problem 2:

    • fg=x4+4x2+11f \circ g = \sqrt{x^4 + 4x^2 + 11}
    • gf=x2+9g \circ f = x^2 + 9

Would you like more details on any of these steps? Here are five related questions for further exploration:

  1. How does the composition of functions relate to transformations in real-world contexts?
  2. What are the properties of function composition in terms of commutativity and associativity?
  3. How can we differentiate or integrate composed functions like fgf \circ g and gfg \circ f?
  4. What are the common errors when dealing with function compositions in algebra?
  5. How would the result change if the functions f(x)f(x) and g(x)g(x) were non-polynomial?

Tip: Always evaluate the inner function first in function compositions (i.e., f(g(x))f(g(x)) means apply g(x)g(x) first, then ff).

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Math Problem Analysis

Mathematical Concepts

Function Composition
Polynomials
Radicals

Formulas

f ∘ g = f(g(x))
g ∘ f = g(f(x))

Theorems

Composition of Functions

Suitable Grade Level

Grades 9-12