Math Problem Statement

Use the pair of functions to find f(g(x)) and g(f(x)) . Simplify your answers.

f(x)=1x−5 , g(x)=9x+5

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

Solution

To find f(g(x))f(g(x)) and g(f(x))g(f(x)), we'll substitute each function into the other.

Given: f(x)=1x5andg(x)=9x+5f(x) = \frac{1}{x} - 5 \quad \text{and} \quad g(x) = 9x + 5

Step 1: Find f(g(x))f(g(x))

  1. Substitute g(x)g(x) into f(x)f(x): f(g(x))=f(9x+5)f(g(x)) = f(9x + 5)
  2. Since f(x)=1x5f(x) = \frac{1}{x} - 5, replace xx in f(x)f(x) with 9x+59x + 5: f(g(x))=19x+55f(g(x)) = \frac{1}{9x + 5} - 5

So, f(g(x))=19x+55f(g(x)) = \frac{1}{9x + 5} - 5

Step 2: Find g(f(x))g(f(x))

  1. Substitute f(x)f(x) into g(x)g(x): g(f(x))=g(1x5)g(f(x)) = g\left(\frac{1}{x} - 5\right)
  2. Since g(x)=9x+5g(x) = 9x + 5, replace xx in g(x)g(x) with 1x5\frac{1}{x} - 5: g(f(x))=9(1x5)+5g(f(x)) = 9\left(\frac{1}{x} - 5\right) + 5
  3. Distribute 99: g(f(x))=9x45+5g(f(x)) = \frac{9}{x} - 45 + 5
  4. Combine like terms: g(f(x))=9x40g(f(x)) = \frac{9}{x} - 40

So, g(f(x))=9x40g(f(x)) = \frac{9}{x} - 40

Final Answers

f(g(x))=19x+55f(g(x)) = \frac{1}{9x + 5} - 5 g(f(x))=9x40g(f(x)) = \frac{9}{x} - 40

Would you like further details or have any questions?

Related Questions

  1. What are the domain restrictions for f(g(x))f(g(x)) and g(f(x))g(f(x))?
  2. How would you find g(g(x))g(g(x)) or f(f(x))f(f(x)) using the same functions?
  3. What are the inverses of f(x)f(x) and g(x)g(x), if they exist?
  4. How would changes in the constants (like 5-5 or +5+5) affect the results?
  5. Can we compose functions in the reverse order, and how does it affect the outcome?

Tip

When composing functions, keep in mind that f(g(x))f(g(x)) and g(f(x))g(f(x)) often have different domains based on the inner functions. Always check for any restrictions before simplifying.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Simplification of Rational Expressions

Formulas

f(g(x)) = f(9x + 5) = 1/(9x + 5) - 5
g(f(x)) = g(1/x - 5) = 9(1/x - 5) + 5 = 9/x - 40

Theorems

Properties of Function Composition

Suitable Grade Level

Grades 10-12