Math Problem Statement

Evaluate (f ∘ g)(-3) and (g ∘ f)(1) where f(x) = 5x - 3 and g(x) = √(x² - 1).

Solution

We are asked to evaluate (fg)(3)(f \circ g)(-3) and (gf)(1)(g \circ f)(1), where:

f(x)=5x3f(x) = 5x - 3 g(x)=x21g(x) = \sqrt{x^2 - 1}

Step 1: Evaluate (fg)(3)(f \circ g)(-3)

This means we first evaluate g(3)g(-3) and then substitute the result into f(x)f(x).

  1. Calculate g(3)g(-3): g(3)=(3)21=91=8g(-3) = \sqrt{(-3)^2 - 1} = \sqrt{9 - 1} = \sqrt{8}

  2. Now, substitute g(3)=8g(-3) = \sqrt{8} into f(x)f(x): f(8)=5(8)3=583f(\sqrt{8}) = 5(\sqrt{8}) - 3 = 5\sqrt{8} - 3

Thus, (fg)(3)=583(f \circ g)(-3) = 5\sqrt{8} - 3.

Step 2: Evaluate (gf)(1)(g \circ f)(1)

This means we first evaluate f(1)f(1) and then substitute the result into g(x)g(x).

  1. Calculate f(1)f(1): f(1)=5(1)3=53=2f(1) = 5(1) - 3 = 5 - 3 = 2

  2. Now, substitute f(1)=2f(1) = 2 into g(x)g(x): g(2)=221=41=3g(2) = \sqrt{2^2 - 1} = \sqrt{4 - 1} = \sqrt{3}

Thus, (gf)(1)=3(g \circ f)(1) = \sqrt{3}.

Final Results:

(fg)(3)=583(f \circ g)(-3) = 5\sqrt{8} - 3 (gf)(1)=3(g \circ f)(1) = \sqrt{3}

Would you like further clarification on any of these steps?

Here are five related questions for further exploration:

  1. How do you find the domain of composite functions like fgf \circ g?
  2. Can you graph f(x)=5x3f(x) = 5x - 3 and g(x)=x21g(x) = \sqrt{x^2 - 1}?
  3. What is the inverse of the function g(x)=x21g(x) = \sqrt{x^2 - 1}?
  4. How do you determine the range of a composite function?
  5. What happens if x=1x = 1 for (fg)(x)(f \circ g)(x)?

Tip: Always check the domain restrictions when dealing with square roots to ensure you're only working with real numbers.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Square Roots

Formulas

f(x) = 5x - 3
g(x) = √(x² - 1)
Composition of functions: (f ∘ g)(x) = f(g(x))

Theorems

Function composition rule

Suitable Grade Level

Grades 10-12