Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 2 - Limits - 2.5 Evaluating Limits Algebraically - Exercises - Page 72: 17

Answer

$$\lim _{x \rightarrow 16} \frac{\sqrt{x}-4}{x-16} =\frac{1}{8}$$

Work Step by Step

Given $$\lim _{x \rightarrow 16} \frac{\sqrt{x}-4}{x-16}$$ let $$ f(x) = \frac{\sqrt{x}-4}{x-16}$$ Since, we have $$ f(4)=\frac{4-4}{16-16}=\frac{0}{0}$$ So, transform algebraically and cancel \begin{aligned} L&=\lim _{x \rightarrow 16} \frac{\sqrt{x}-4}{x-16}\\ &= \lim _{x \rightarrow 16} \frac{\sqrt{x}-4}{x-16} \ \ \frac{\sqrt{x}+4}{\sqrt{x}+4}\\ &= \lim _{x \rightarrow 16} \frac{( x-16) }{( x-16)(\sqrt{x}+4)} \ \\ &=\lim _{x \rightarrow 16} \frac{1}{\sqrt{x}+4 }\\ &=\frac{1}{4+4}\\ &=\frac{1}{8}\\ \end{aligned}
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