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: 22

Answer

$\lim_{x\to1}\dfrac{x^{3}-1}{x^{2}-1}=\dfrac{3}{2}$

Work Step by Step

$\lim_{x\to1}\dfrac{x^{3}-1}{x^{2}-1}$ Try to evaluate the limit applying direct substitution: $\lim_{x\to1}\dfrac{x^{3}-1}{x^{2}-1}=\dfrac{1^{3}-1}{1^{2}-1}=\dfrac{0}{0}$ Indeterminate form The limit could not be evaluated using direct substitution. Factor the numerator and the denominator of the function and simplify: $\lim_{x\to1}\dfrac{x^{3}-1}{x^{2}-1}=\lim_{x\to1}\dfrac{(x-1)(x^{2}+x+1)}{(x-1)(x+1)}=...$ $...=\lim_{x\to1}\dfrac{x^{2}+x+1}{x+1}=...$ Try direct substitution again: $...=\lim_{x\to1}\dfrac{x^{2}+x+1}{x+1}=\dfrac{1^{2}+1+1}{1+1}=\dfrac{3}{2}$
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