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: 14

Answer

$$\lim _{h \rightarrow 0} \frac{(3+h)^3-27}{h}=27$$

Work Step by Step

Given $$\lim _{h \rightarrow 0} \frac{(3+h)^3-27}{h}$$ let $$ f(h) = \frac{(3+h)^3-27}{h}$$ Since, we have $$ f(0)=\frac{27-27}{0}=\frac{0}{0}$$ So, transform algebraically and cancel \begin{aligned} L&=\lim _{h \rightarrow 0} \frac{(3+h)^3-3}{h}\\ &= \lim _{h \rightarrow 0} \frac{27+9h^2+27h+h^3-27}{h}\\ &= \lim _{h \rightarrow 0} \frac{9h^2+27h+h^3}{h}\\ &= \lim _{h \rightarrow 0} \frac{h(9h+27+h^2)}{h}\\ &= \lim _{h \rightarrow 0}(9h+27+h^2)\\ &=0+27+0\\ &= 27 \end{aligned}
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