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: 16

Answer

$$\lim _{h \rightarrow 4} \frac{(h+2)^2-9h}{h-4}=3$$

Work Step by Step

Given $$\lim _{h \rightarrow 4} \frac{(h+2)^2-9h}{h-4}$$ let $$ f(h) = \frac{(h+2)^2-9h}{h-4}$$ Since, we have $$ f(4)=\frac{36-36}{4-4}=\frac{0}{0}$$ So, transform algebraically and cancel \begin{aligned} L&=\lim _{h \rightarrow 4} \frac{(h+2)^2-9h}{h-4}\\ &= \lim _{h \rightarrow 4} \frac{h^2+4h+4-9h}{h-4}\\ &= \lim _{h \rightarrow 4} \frac{h^2-5h+4}{h-4}\\ &= \lim _{h \rightarrow 4} \frac{(h-4)(h-1)}{h-4}\\ &= \lim _{h \rightarrow 0}(h-1)\\ &=4-1\\ &= 3 \end{aligned}
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