Math Problem Statement

Find the rules for the composite functions f ∘ g and g ∘ f.

f(x) = 

sqrtx + 8

g(x) = 

1/

x − 8

Solution

Let's first define the functions you gave:

  • f(x)=x+8f(x) = \sqrt{x} + 8
  • g(x)=1x8g(x) = \frac{1}{x} - 8

Now, let's compute the two composite functions fgf \circ g and gfg \circ f.

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

This means we need to substitute g(x)g(x) into f(x)f(x).

From the definition of f(x)f(x), we have: f(x)=x+8f(x) = \sqrt{x} + 8

To compute f(g(x))f(g(x)), substitute g(x)=1x8g(x) = \frac{1}{x} - 8 into f(x)f(x): f(g(x))=1x8+8f(g(x)) = \sqrt{ \frac{1}{x} - 8 } + 8

So: (fg)(x)=1x8+8(f \circ g)(x) = \sqrt{ \frac{1}{x} - 8 } + 8

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

This means we need to substitute f(x)f(x) into g(x)g(x).

From the definition of g(x)g(x), we have: g(x)=1x8g(x) = \frac{1}{x} - 8

Now, substitute f(x)=x+8f(x) = \sqrt{x} + 8 into g(x)g(x): g(f(x))=1x+88g(f(x)) = \frac{1}{\sqrt{x} + 8} - 8

So: (gf)(x)=1x+88(g \circ f)(x) = \frac{1}{\sqrt{x} + 8} - 8

Final Answers:

  • (fg)(x)=1x8+8(f \circ g)(x) = \sqrt{ \frac{1}{x} - 8 } + 8
  • (gf)(x)=1x+88(g \circ f)(x) = \frac{1}{\sqrt{x} + 8} - 8

Let me know if you need further details or clarifications on these composite functions!

Related Questions:

  1. How do I determine the domain of a composite function?
  2. How can I find the inverse of a composite function?
  3. What are the differences between f(x)g(x)f(x) \circ g(x) and g(x)f(x)g(x) \circ f(x)?
  4. How can I graph the composite functions fgf \circ g and gfg \circ f?
  5. Can I simplify the expressions for (fg)(x)(f \circ g)(x) and (gf)(x)(g \circ f)(x)?

Tip: When working with composite functions, always remember to check the domains of the individual functions and how they interact to affect the overall domain of the composite function.

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Math Problem Analysis

Mathematical Concepts

Functions
Composite Functions
Algebra

Formulas

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

Theorems

Function Composition Rules

Suitable Grade Level

Grades 10-12