Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 1 - Functions and Limits - 1.6 Calculating Limits Using the Limit Laws - 1.6 Exercises - Page 70: 2

Answer

the graphs of f and g are given, use them to evaluate each limit if it exists. If the limit does not exist, explain why. (a) 1 (b) the limit of the difference does not exist because g(x) doesn't have limit (c) 2 (d) The limit of the quotient doesn't exist because the denominator is 0 (e) -4 (f) 5

Work Step by Step

(a) $\lim \limits_{x \to 2}[f(x) + g(x)] $ Apply the sum law $$\lim \limits_{x \to 2}f(x) + \lim \limits_{x \to 2} g(x)= -1 + 2 = 1 $$ (b) $\lim\limits_{x \to 0} [f(x) - g(x)]$ Apply the difference law $$\lim\limits_{x \to 0} f(x) - \lim\limits_{x \to 0} g(x) = 2 - \nexists$$ Because the limit of $g(x)$ (given the graph) doesn't exist, the difference with $f(x)$ and $g(x)$ don't exist The limit doesn't exist (c) $\lim\limits_{x \to -1} [f(x) *g(x)]$ Apply the product law $$\lim\limits_{x \to -1} f(x) *\lim\limits_{x \to -1}g(x) = 1 * 2=2$$ (d) $\lim\limits_{x \to 3} [\frac{f(x)}{g(x)}]$ Apply the quotient law $$\frac{\lim\limits_{x \to 3} f(x)}{\lim\limits_{x \to 3} g(x)}= \frac{1}{0} = \nexists$$ the limit doesn't exist because $g(x)\neq 0$ (e) $\lim\limits_{x \to 2} [x^2*f(x)]$ Apply the product law Note: $x^2 $is just other function $$\lim\limits_{x \to 2} x^2*\lim\limits_{x \to 2} f(x) = (2)^2 * (-1) = 4*(-1) = -4$$ (f) $f(-1) + \lim\limits_{x \to -1} g(x) $ Apply the sum law Note: the function at $x=-1$ is defined at $3$. We can substitute $$3 + 2 =5$$
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