Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 3 - The Derivative - 3.1 Limits - 3.1 Exercises - Page 137: 56

Answer

$$ g(x)=\left\{\begin{array}{ll}{5} & {\text { if } x<0} \\ {x^{2}-2} & {\text { if } 0 \leq x \leq 3} \\ {7} & {\text { if } x>3}\end{array}\right. $$ We obtain that: (a) $$\lim _{x \rightarrow 0} g(x) $$ does not exist since $$ \lim _{x \rightarrow 0^{+}} g(x) \neq \lim _{x \rightarrow 0^{-}} g(x) $$ (b) $$ \lim _{x \rightarrow 3} g(x)=7 $$

Work Step by Step

$$ g(x)=\left\{\begin{array}{ll}{5} & {\text { if } x<0} \\ {x^{2}-2} & {\text { if } 0 \leq x \leq 3} \\ {7} & {\text { if } x>3}\end{array}\right. $$ A function $g(x)$ defined by two or more cases is called a piecewise function. The domain of $g(x)$ is all real numbers. To determine the limit as $x$ approaches 0, 3, we are concerned only with the values of $g(x)$ when $x$ is close but not equal to 0 , 3 Once again, (a) $$ \lim _{x \rightarrow 0^{-}} g(x)=5 $$ and $$ \lim _{x \rightarrow 0^{+}} g(x)=-2 $$ Therefore $$\lim _{x \rightarrow 0} g(x) $$ does not exist since $$ \lim _{x \rightarrow 0^{+}} g(x) \neq \lim _{x \rightarrow 0^{-}} g(x) $$ (b) $$ \lim _{x \rightarrow 3^{-}} g(x)=7 $$ and $$ \lim _{x \rightarrow 3^{+}} g(x)=7 $$ Therefore $$ \lim _{x \rightarrow 3} g(x)=7 $$
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