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 216: 16

Answer

$(f+g)(x) =\displaystyle \frac{x+2}{x+1}$, domain: $(-\infty,-1)\cup(-1,+\infty).$ $(f-g)(x) =\displaystyle \frac{2-x}{x+1}$, domain: $(-\infty,-1)\cup(-1,+\infty).$ $(fg)(x) =\displaystyle \frac{2x}{(x+1)^{2}}$, domain: $(-\infty,-1)\cup(-1,+\infty).$ $(\displaystyle \frac{f}{g})(x) =\frac{2}{x}$ , domain: $(-\infty,-1)\cup(-1,0)\cup(0,+\infty)$

Work Step by Step

The domain of f is $\{x|x\neq-1\}$, because f is defined only for x that yield a nonzero number in the denominator. The domain of g is $\{x|x\neq-1\}$, for the same reason. Their intersection is $\{x|x\neq-1\}= (-\infty,-1)\cup(-1,+\infty)$ $(f+g)(x)=\displaystyle \frac{2}{x+1}+\frac{x}{x+1} =\displaystyle \frac{x+2}{x+1}$, domain: $(-\infty,-1)\cup(-1,+\infty).$ $(f-g)(x)=\displaystyle \frac{2}{x+1}-\frac{x}{x+1} =\displaystyle \frac{2-x}{x+1}$, domain: $(-\infty,-1)\cup(-1,+\infty).$ $(fg)(x)=\displaystyle \frac{2}{x+1}\cdot\frac{x}{x+1} =\displaystyle \frac{2x}{(x+1)^{2}}$, domain: $(-\infty,-1)\cup(-1,+\infty).$ $(\displaystyle \frac{f}{g})(x)=\frac{\frac{2}{x+1}}{\frac{x}{x+1}}=\frac{2(x+1)}{x(x+1)}=\frac{2}{x}$ , domain: $\{x|x\neq-1,x\neq 0\}=(-\infty,-1)\cup(-1,0)\cup(0,+\infty)$
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