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 2.3 - The Precise Definition of a Limit - Exercises 2.3 - Page 67: 53

Answer

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Work Step by Step

Step 1. Identify the statement in the Exercise: "The number $L$ is the limit of $ƒ(x)$ as $x$ approaches $c$ if $ƒ(x)$ gets closer to $L$ as $x$ approaches $c$." Step 2. Recall the definition of a limit: We say that $\lim_{x\to c}f(x)=L$ the limit of $fx)$ as $x$ approaches $0$ is the number $L$, if, for every number $\epsilon\gt0$, there exists a corresponding number $\delta\gt0$ such that for all $x$, $0\lt |x-c| \lt \delta$, we get $|f(x)-L|\lt\epsilon$. Step 3. Comparing the above two statements, we find that the first statement contains flaws such as it does not state that function $f(x)$ can get any close to $L$ and in both directions. Step 4. For example, with a simple function $f(x)=x$, we can say $f(x)$ gets close to $L=0$ when $x$ approaches $c=0.1$ from a starting value of $1$, but the limit is not $0$ when $x\to 0.1$, instead we have $\lim_{x\to 0.1}f(x)=\lim_{x\to 0.1}x=0.1\ne L$
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