Math Problem Statement

Use the pair of functions to find f(g(x)) and g(f(x))

. Simplify your answers.   f(x)=1/(x−6)

g(x)=(8/x)+6

Solution

Let's find f(g(x))f(g(x)) and g(f(x))g(f(x)) step by step, using the given functions.

Given:

  1. f(x)=1x6f(x) = \frac{1}{x - 6}
  2. g(x)=8x+6g(x) = \frac{8}{x} + 6

Finding f(g(x))f(g(x)):

We want to substitute g(x)g(x) into f(x)f(x). That is, we replace xx in f(x)f(x) with g(x)g(x).

f(g(x))=f(8x+6)=1(8x+6)6f(g(x)) = f\left( \frac{8}{x} + 6 \right) = \frac{1}{\left( \frac{8}{x} + 6 \right) - 6}

Simplify the expression inside the parentheses:

8x+66=8x\frac{8}{x} + 6 - 6 = \frac{8}{x}

So, now we have:

f(g(x))=18x=x8f(g(x)) = \frac{1}{\frac{8}{x}} = \frac{x}{8}

Thus, f(g(x))=x8f(g(x)) = \frac{x}{8}.


Finding g(f(x))g(f(x)):

We now substitute f(x)f(x) into g(x)g(x). That is, we replace xx in g(x)g(x) with f(x)f(x).

g(f(x))=g(1x6)=81x6+6g(f(x)) = g\left( \frac{1}{x - 6} \right) = \frac{8}{\frac{1}{x - 6}} + 6

Simplify the first term:

81x6=8(x6)\frac{8}{\frac{1}{x - 6}} = 8(x - 6)

Now, add 6:

g(f(x))=8(x6)+6=8x48+6=8x42g(f(x)) = 8(x - 6) + 6 = 8x - 48 + 6 = 8x - 42

Thus, g(f(x))=8x42g(f(x)) = 8x - 42.


Final Answers:

  1. f(g(x))=x8f(g(x)) = \frac{x}{8}
  2. g(f(x))=8x42g(f(x)) = 8x - 42

Would you like any further details on these steps?


Here are 5 related questions to expand on this concept:

  1. What happens if we reverse the order of composition for different functions?
  2. How would the composition change if f(x)f(x) or g(x)g(x) were different?
  3. Can we find the inverse of either function?
  4. What would f(g(x))f(g(x)) look like if both functions were polynomials?
  5. How do you interpret the composition of two functions geometrically?

Tip: When composing functions, always substitute the entire output of the inner function into the outer function's variable.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Rational Functions

Formulas

f(x) = 1 / (x - 6)
g(x) = (8 / x) + 6
f(g(x)) = f(g(x)) = 1 / [(8/x) + 6 - 6]
g(f(x)) = 8 / [1 / (x - 6)] + 6

Theorems

Function Composition

Suitable Grade Level

Grades 10-12