Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 13 - Section 13.2 - Finding Limits Algebraically - 13.2 Exercises - Page 913: 3

Answer

(a) $2$ (b) Does not exist. (c) $0$ (d) Does not exist. (e) $16$ (f) $2$

Work Step by Step

(a) Based on the graph, we have $$\lim_{x\to 2}[f(x)+g(x)]=\lim_{x\to 2}f(x)+\lim_{x\to 2}g(x)=2+0=2$$ (b) $$\lim_{x\to 1}[f(x)+g(x)]=\lim_{x\to 1}f(x)+\lim_{x\to 1}g(x)$$ As $$\lim_{x\to 1^-}g(x)\ne \lim_{x\to 1^+}g(x)$$ $$\lim_{x\to 1}g(x)$$ does not exist, and thus $$\lim_{x\to 1}[f(x)+g(x)]$$ does not exist. (c) $$\lim_{x\to 0}[f(x)g(x)]=\lim_{x\to 0}f(x)\cdot\lim_{x\to 0}g(x)=0\times1.5=0$$ (d) $$\lim_{x\to -1}\frac{f(x)}{g(x)}=\frac{\lim_{x\to -1}f(x)}{\lim_{x\to -1}g(x)} $$ However, as $$\lim_{x\to -1}g(x)=0$$ the limit for this part of the question does not exist. (e) $$\lim_{x\to 2}x^3f(x)=\lim_{x\to 2}x^3\cdot\lim_{x\to 2}f(x)=2^3\times2=16$$ (f) $$\lim_{x\to 1}\sqrt {3+f(x)}=\sqrt {3+\lim_{x\to 1}f(x)}=\sqrt {3+1}=2$$
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