Math Problem Statement

Find each of the following, if possible (if not possible, enter NONE): (a) f ∘ g (b) g ∘ f, where f(x) = √(x - 1) and g(x) = x^3 + 1.

Solution

The problem in the image asks to find the following compositions of functions, given the definitions:

  • f(x)=x1f(x) = \sqrt{x - 1}
  • g(x)=x3+1g(x) = x^3 + 1

You are tasked with finding fgf \circ g and gfg \circ f.

(a) fg(x)f \circ g(x)

This means applying g(x)g(x) first, then applying f(x)f(x) to the result: fg(x)=f(g(x))=f(x3+1)f \circ g(x) = f(g(x)) = f(x^3 + 1) Now substitute x3+1x^3 + 1 into f(x)f(x): f(x3+1)=(x3+1)1=x3f(x^3 + 1) = \sqrt{(x^3 + 1) - 1} = \sqrt{x^3} So, fg(x)=x3f \circ g(x) = \sqrt{x^3} This simplifies to x3/2|x^{3/2}|, but in many cases, x3\sqrt{x^3} will be an acceptable answer.

(b) gf(x)g \circ f(x)

This means applying f(x)f(x) first, then applying g(x)g(x) to the result: gf(x)=g(f(x))=g(x1)g \circ f(x) = g(f(x)) = g(\sqrt{x - 1}) Now substitute x1\sqrt{x - 1} into g(x)g(x): g(x1)=(x1)3+1=(x1)3/2+1g(\sqrt{x - 1}) = (\sqrt{x - 1})^3 + 1 = (x - 1)^{3/2} + 1 So, gf(x)=(x1)3/2+1g \circ f(x) = (x - 1)^{3/2} + 1

These are the compositions of the two functions.

Would you like a detailed explanation or have any questions about these steps? Here are some related questions for further practice:

  1. What is the domain of fg(x)f \circ g(x)?
  2. What is the domain of gf(x)g \circ f(x)?
  3. How would you compute f(f(x))f(f(x))?
  4. How would you compute g(g(x))g(g(x))?
  5. What would happen if g(x)=x+1g(x) = \sqrt{x} + 1? How would that affect the compositions?

Tip: When working with function composition, always check the domains of both functions to ensure that the composition is defined.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Square Roots
Cubic Functions

Formulas

f(x) = √(x - 1)
g(x) = x^3 + 1
f ∘ g(x) = √((x^3 + 1) - 1) = √(x^3)
g ∘ f(x) = ((√(x - 1))^3) + 1 = (x - 1)^(3/2) + 1

Theorems

Function Composition
Domain Restrictions

Suitable Grade Level

High School (Grades 9-12)