Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 2 - Section 2.7 - Combining Functions - 2.7 Exercises - Page 217: 57

Answer

f∘g $\frac {1}{x+1}$ Domain: (-∞, -1) U (-1,0) U (0, ∞) g∘f $\frac {x+1}{x} $Domain: (-∞, -1) U (-1,0) U (0, ∞) f∘f $\frac{x}{2x+1}$ Domain: (-∞, -1) U (-1,-1/2) U (-1/2, ∞) g∘g $x$ Domain: (- ∞, 0) U (0, ∞)

Work Step by Step

$f(x) = \frac{x}{x+1}$ $g(x) = \frac{1}{x} $ f∘g $f(\frac{1}{x}) = \frac {\frac {1}{x}} {\frac {1}{x} + 1}$ = $\frac {1}{x+1}$ Domain: (-∞, -1) U (-1,0) U (0, ∞) g∘f $g(\frac{x}{x+1}) = \frac{1}{\frac{x}{x+1}}$ = $\frac {x+1}{x} $Domain: (-∞, -1) U (-1,0) U (0, ∞) f∘f $f(\frac{x}{x+1}) = \frac{\frac{x}{x+1}}{\frac{x}{x+1} + 1}$ =$\frac{x}{x + 1(x+1)}$ =$\frac{x}{2x+1}$ Domain: (-∞, -1) U (-1,-1/2) U (-1/2, ∞) g∘g $g(\frac{1}{x}) = \frac{1}{\frac{1}{x}}$ =x Domain: (- ∞, 0) U (0, ∞)
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