Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 2: Limits and Continuity - Section 2.6 - Limits Involving Infinity; Asymptotes of Graphs - Exercises 2.6 - Page 98: 57

Answer

a. $-\infty$ b. $\frac{1}{4}$ c. $\frac{1}{4}$ d. $\frac{1}{4}$ e. $-\infty$

Work Step by Step

a. We have $x\to0^+,x\ne0$, $\lim_{x\to0^+}\frac{x^2-3x+2}{x^3-2x^2}=\lim_{x\to0^+}\frac{x^2-3x+2}{x^2(x-2)}=\lim_{x\to0^+}\frac{1}{x^2}\frac{0^2-0+2}{0-2}=-\lim_{x\to0^+}\frac{1}{x^2}=-\infty$ b. We have $x\to2^+,x\ne2$, $\lim_{x\to2^+}\frac{x^2-3x+2}{x^3-2x^2}=\lim_{x\to2^+}\frac{(x-1)(x-2)}{x^2(x-2)}=\lim_{x\to2^+}\frac{x-1}{x^2}=\frac{2-1}{2^2}=\frac{1}{4}$ c. We have $x\to2^-,x\ne2$, $\lim_{x\to2^-}\frac{x^2-3x+2}{x^3-2x^2}=\lim_{x\to2^-}\frac{(x-1)(x-2)}{x^2(x-2)}=\lim_{x\to2^-}\frac{x-1}{x^2}=\frac{2-1}{2^2}=\frac{1}{4}$ d. Since $\lim_{x\to2^+}\frac{x^2-3x+2}{x^3-2x^2}=\lim_{x\to2^-}\frac{x^2-3x+2}{x^3-2x^2}$, we have $\lim_{x\to2}\frac{x^2-3x+2}{x^3-2x^2}=\frac{1}{4}$ e. We have $x\to0, x\ne0$, $\lim_{x\to0}\frac{x^2-3x+2}{x^3-2x^2}=\lim_{x\to0}\frac{x^2-3x+2}{x^2(x-2)}=\lim_{x\to0}\frac{1}{x^2}\frac{0^2-0+2}{0-2}=-\lim_{x\to0}\frac{1}{x^2}=-\infty$
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