Math Problem Statement

Consider the functions f(x) = 8^x and g(x) = x^8. Determine the following compositions of functions: (f ∘ f)(x), (f ∘ g)(x), (g ∘ f)(x), and (g ∘ g)(x).

Solution

Let's break down the compositions of functions based on the given definitions of f(x)=8xf(x) = 8^x and g(x)=x8g(x) = x^8.

1. (ff)(x)=f(f(x))(f \circ f)(x) = f(f(x))

  • We know that f(x)=8xf(x) = 8^x, so f(f(x))=f(8x)f(f(x)) = f(8^x).
  • Applying ff again to 8x8^x, we get: f(8x)=88x.f(8^x) = 8^{8^x}. Thus, (ff)(x)=88x(f \circ f)(x) = 8^{8^x}.

2. (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x))

  • Since g(x)=x8g(x) = x^8, we substitute g(x)g(x) into f(x)f(x): f(g(x))=f(x8)=8x8.f(g(x)) = f(x^8) = 8^{x^8}. Thus, (fg)(x)=8x8(f \circ g)(x) = 8^{x^8}.

3. (gf)(x)=g(f(x))(g \circ f)(x) = g(f(x))

  • Since f(x)=8xf(x) = 8^x, we substitute f(x)f(x) into g(x)g(x): g(f(x))=g(8x)=(8x)8=88x.g(f(x)) = g(8^x) = (8^x)^8 = 8^{8x}. Thus, (gf)(x)=88x(g \circ f)(x) = 8^{8x}.

4. (gg)(x)=g(g(x))(g \circ g)(x) = g(g(x))

  • We know that g(x)=x8g(x) = x^8, so g(g(x))=g(x8)=(x8)8=x64g(g(x)) = g(x^8) = (x^8)^8 = x^{64}. Thus, (gg)(x)=x64(g \circ g)(x) = x^{64}.

Summary of Results:

  1. (ff)(x)=88x(f \circ f)(x) = 8^{8^x}
  2. (fg)(x)=8x8(f \circ g)(x) = 8^{x^8}
  3. (gf)(x)=88x(g \circ f)(x) = 8^{8x}
  4. (gg)(x)=x64(g \circ g)(x) = x^{64}

Would you like further details or clarifications on any of these steps?

Here are some related questions to consider:

  1. How do the rules for function composition work in general?
  2. What are the differences between composing functions and multiplying them?
  3. How does the composition of exponential functions behave compared to other types of functions?
  4. What are the domain restrictions for these compositions?
  5. How would the compositions change if f(x)f(x) and g(x)g(x) had different base forms?

Tip: Always evaluate the inner function first when performing function composition.

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Math Problem Analysis

Mathematical Concepts

Algebra
Functions
Exponential Functions
Function Composition

Formulas

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

Theorems

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Suitable Grade Level

Grades 9-12