Math Problem Statement

Find f​(g​(x​)) and g​(f​(x​)) and determine whether the pair of functions f and g are inverses of each other. f left parenthesis x right parenthesis equals StartFraction 8 Over x minus 7 EndFraction    and   g left parenthesis x right parenthesis equals StartFraction 8 Over x EndFraction plus 7

Solution

We are given the functions:

f(x)=8x7f(x) = \frac{8}{x - 7} and g(x)=8x+7g(x) = \frac{8}{x} + 7

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

We substitute g(x)g(x) into f(x)f(x):

f(g(x))=f(8x+7)f(g(x)) = f\left( \frac{8}{x} + 7 \right) Now, substitute 8x+7\frac{8}{x} + 7 into the formula for f(x)f(x):

f(8x+7)=8(8x+7)7f\left( \frac{8}{x} + 7 \right) = \frac{8}{\left( \frac{8}{x} + 7 \right) - 7}

Simplify the denominator:

f(g(x))=88x+77=88x=xf(g(x)) = \frac{8}{\frac{8}{x} + 7 - 7} = \frac{8}{\frac{8}{x}} = x

So, f(g(x))=xf(g(x)) = x.

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

We now substitute f(x)f(x) into g(x)g(x):

g(f(x))=g(8x7)g(f(x)) = g\left( \frac{8}{x - 7} \right) Substitute 8x7\frac{8}{x - 7} into the formula for g(x)g(x):

g(8x7)=88x7+7g\left( \frac{8}{x - 7} \right) = \frac{8}{\frac{8}{x - 7}} + 7

Simplify:

g(f(x))=x7+7=xg(f(x)) = x - 7 + 7 = x

So, g(f(x))=xg(f(x)) = x.

Step 3: Conclusion

Since both f(g(x))=xf(g(x)) = x and g(f(x))=xg(f(x)) = x, the functions ff and gg are inverses of each other.


Would you like further details or clarifications on this solution?

Here are 5 related questions for practice:

  1. Find the inverse of f(x)=10x+2f(x) = \frac{10}{x + 2}.
  2. Verify if f(x)=2x+1f(x) = 2x + 1 and g(x)=x12g(x) = \frac{x - 1}{2} are inverses.
  3. Find f(g(x))f(g(x)) for f(x)=3x4f(x) = 3x - 4 and g(x)=x+43g(x) = \frac{x + 4}{3}.
  4. Prove that f(x)=1xf(x) = \frac{1}{x} is its own inverse.
  5. Solve f(g(x))=3f(g(x)) = 3 for f(x)=6x+1f(x) = \frac{6}{x + 1} and g(x)=6x1g(x) = \frac{6}{x - 1}.

Tip: If f(g(x))=g(f(x))=xf(g(x)) = g(f(x)) = x, then ff and gg are guaranteed to be inverses.

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Math Problem Analysis

Mathematical Concepts

Algebra
Inverse Functions
Function Composition

Formulas

f(x) = 8/(x - 7)
g(x) = 8/x + 7
f(g(x)) = x
g(f(x)) = x

Theorems

If f(g(x)) = x and g(f(x)) = x, then f and g are inverses of each other.

Suitable Grade Level

Grades 10-12