Math Problem Statement

If f(x)=1/x-5 and g(x)=1/x-5 (a) f(g(x))=f(g(x))= (b) g(f(x))=

Solution

Let's go step by step to solve these compositions.

Given:
f(x)=1x5f(x) = \frac{1}{x} - 5
g(x)=1x5g(x) = \frac{1}{x} - 5

We need to determine:
(a) f(g(x))f(g(x))
(b) g(f(x))g(f(x))


(a) f(g(x))f(g(x))

By definition of function composition, f(g(x))f(g(x)) means substituting g(x)g(x) into f(x)f(x).

So:
f(g(x))=f(1x5)f(g(x)) = f\left(\frac{1}{x} - 5\right)

Now substitute 1x5\frac{1}{x} - 5 in place of xx in f(x)=1x5f(x) = \frac{1}{x} - 5:
f(1x5)=11x55f\left(\frac{1}{x} - 5\right) = \frac{1}{\frac{1}{x} - 5} - 5

To simplify, let u=1x5u = \frac{1}{x} - 5. Then: 1u=11x5=x15x\frac{1}{u} = \frac{1}{\frac{1}{x} - 5} = \frac{x}{1 - 5x}

Thus: f(g(x))=x15x5f(g(x)) = \frac{x}{1 - 5x} - 5


(b) g(f(x))g(f(x))

Similarly, g(f(x))g(f(x)) means substituting f(x)f(x) into g(x)g(x).

So:
g(f(x))=g(1x5)g(f(x)) = g\left(\frac{1}{x} - 5\right)

Now substitute 1x5\frac{1}{x} - 5 in place of xx in g(x)=1x5g(x) = \frac{1}{x} - 5:
g(1x5)=11x55g\left(\frac{1}{x} - 5\right) = \frac{1}{\frac{1}{x} - 5} - 5

Following the same steps as above, we get: g(f(x))=x15x5g(f(x)) = \frac{x}{1 - 5x} - 5


Final Results:

(a) f(g(x))=x15x5f(g(x)) = \frac{x}{1 - 5x} - 5
(b) g(f(x))=x15x5g(f(x)) = \frac{x}{1 - 5x} - 5


Do you need further clarifications or a more detailed breakdown of the steps?


Here are 5 related questions to explore further:

  1. What are the domains of f(x)f(x) and g(x)g(x)?
  2. How would the compositions change if f(x)=1x+5f(x) = \frac{1}{x + 5}?
  3. What is the inverse function of f(x)=1x5f(x) = \frac{1}{x} - 5?
  4. Are ff and gg bijective functions?
  5. How do compositions behave when both functions are identical?

Tip: When simplifying complex fractions, multiply the numerator and denominator by the least common denominator to avoid mistakes.

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Math Problem Analysis

Mathematical Concepts

Algebra
Function Composition

Formulas

f(g(x)) = f(1/x - 5)
g(f(x)) = g(1/x - 5)

Theorems

Composition of Functions

Suitable Grade Level

Grades 10-12