Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 2 - Section 2.3 - Calculating Limits Using the Limit Laws - 2.3 Exercises - Page 104: 55

Answer

$\lim\limits_{x \to 2}f(x) = -1$ $f(2) = 0$ $\lim\limits_{x \to 2}f(x) \neq f(2)$

Work Step by Step

$f(x) = \lfloor{x}\rfloor + \lfloor{-x}\rfloor$ We can find $f(2)$: $f(2) = \lfloor{2}\rfloor + \lfloor{-2}\rfloor$ $f(2) = 2 + (-2)$ $f(2) = 0$ We can find $\lim\limits_{x \to 2^-}f(x)$: $\lim\limits_{x \to 2^-}(\lfloor{x}\rfloor + \lfloor{-x}\rfloor)$ $=\lim\limits_{x \to 2^-}\lfloor{x}\rfloor +\lim\limits_{x \to 2^-}\lfloor{-x}\rfloor$ $=\lim\limits_{x \to 2^-}1 +\lim\limits_{x \to 2^-}-2$ $= 1+(-2)$ $= -1$ We can find $\lim\limits_{x \to 2^+}f(x)$: $\lim\limits_{x \to 2^+}(\lfloor{x}\rfloor + \lfloor{-x}\rfloor)$ $=\lim\limits_{x \to 2^+}\lfloor{x}\rfloor +\lim\limits_{x \to 2^+}\lfloor{-x}\rfloor$ $=\lim\limits_{x \to 2^+}2 +\lim\limits_{x \to 2^+}-3$ $= 2+(-3)$ $= -1$ Since $\lim\limits_{x \to 2^-}f(x) = \lim\limits_{x \to 2^+}f(x)$, then $\lim\limits_{x \to 2}f(x)$ exists. However, $\lim\limits_{x \to 2}f(x) = -1$ but $f(2) = 0$ That is, $\lim\limits_{x \to 2}f(x) \neq f(2)$
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