Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 13 - Section 13.2 - Finding Limits Algebraically - 13.2 Exercises - Page 913: 34

Answer

$\lim_{x\to0}\dfrac{(4+x)^{3}-64}{x}=48$ The graph is shown below:

Work Step by Step

$\lim_{x\to0}\dfrac{(4+x)^{3}-64}{x}$ Try to evaluate the limit applying direct substitution: $\lim_{x\to0}\dfrac{(4+x)^{3}-64}{x}=\dfrac{(4+0)^{3}-64}{0}=\dfrac{0}{0}$ Indeterminate form. The limit could not be evaluated using direct substitution. Factor the numerator and simplify: $\lim_{x\to0}\dfrac{(4+x)^{3}-64}{x}=...$ $...=\lim_{x\to0}\dfrac{[(4+x)-4][(4+x)^{2}+4(4+x)+4^{2}]}{x}=...$ $...=\lim_{x\to0}\dfrac{(x)[(4+x)^{2}+4(4+x)+16]}{x}=...$ $...=\lim_{x\to0}[(4+x)^{2}+4(4+x)+16]=...$ Try to evaluate the limit using direct substitution again: $...=\lim_{x\to0}[(4+x)^{2}+4(4+x)+16]=...$ $...=(4+0)^{2}+4(4+0)+16=16+16+16=48$
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