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: 55

Answer

$$ f(x)=\left\{\begin{array}{ll}{x-1} & {\text { if } x<3} \\ { 2} & {\text { if } 3 \leq x \leq 5} \\ {x+3} & {\text { if } x>5}\end{array}\right. $$ We obtain that: (a) $$ \lim _{x \rightarrow 3} f(x) =2 $$ (b) $$ \lim _{x \rightarrow 5} f(x) $$ does not exist since $$ \lim _{x \rightarrow 5^{+}} f(x) \neq \lim _{x \rightarrow 5^{-}} f(x) $$

Work Step by Step

$$ f(x)=\left\{\begin{array}{ll}{x-1} & {\text { if } x<3} \\ { 2} & {\text { if } 3 \leq x \leq 5} \\ {x+3} & {\text { if } x>5}\end{array}\right. $$ A function $f(x)$ defined by two or more cases is called a piecewise function. The domain of $f(x)$ is all real numbers. To determine the limit as $x$ approaches 0, 3, we are concerned only with the values of $f(x)$ when $x$ is close but not equal to 3 , 5 Once again, (a) $$ \lim _{x \rightarrow 3^{-}} f(x)=2 $$ and $$ \lim _{x \rightarrow 3^{+}} f(x)=2 $$ Therefore $$ \lim _{x \rightarrow 3} f(x) =2 $$ (b) $$ \lim _{x \rightarrow 5^{-}} f(x)=2 $$ and $$ \lim _{x \rightarrow 5^{+}} f(x)=8 $$ Therefore $$ \lim _{x \rightarrow 5} f(x) $$ does not exist since $$ \lim _{x \rightarrow 5^{+}} f(x) \neq \lim _{x \rightarrow 5^{-}} f(x) $$
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