Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 11 - Section 11.1 - Finding Limits Using Tables and Graphs - Exercise Set - Page 1139: 40

Answer

For $ f\left( x \right)=\frac{1}{{{x}^{2}}}$, $\underset{x\to -1}{\mathop{\lim }}\,f\left( x \right)=1$.

Work Step by Step

Consider the function, $ y=\frac{1}{{{x}^{2}}}$ Limits has the following property. $\underset{x\to a}{\mathop{\lim }}\,f\left( x \right)=L $ if and only if $\underset{x\to {{a}^{-}}}{\mathop{\lim }}\,f\left( x \right)=L $ and $\underset{x\to {{a}^{+}}}{\mathop{\lim }}\,f\left( x \right)=L $. For $\underset{x\to -{{1}^{-}}}{\mathop{\lim }}\,f\left( x \right)$, Approach the point $ x=-1$ on the graph from the left side; the value of the $ y-$coordinate approaches to $1$. So, $\underset{x\to -{{1}^{-}}}{\mathop{\lim }}\,f\left( x \right)=1$. For $\underset{x\to -{{1}^{+}}}{\mathop{\lim }}\,f\left( x \right)$, Now approach the point from the right side. As the point is reached, the value of the $ y-$coordinate approaches to $1$. So, $\underset{x\to -{{1}^{+}}}{\mathop{\lim }}\,f\left( x \right)=1$. Since, $\underset{x\to -{{1}^{+}}}{\mathop{\lim }}\,f\left( x \right)=\underset{x\to -{{1}^{-}}}{\mathop{\lim }}\,f\left( x \right)=1$, the value for the given limit exists and is given by, $\underset{x\to -1}{\mathop{\lim }}\,\frac{1}{{{x}^{2}}}=1$
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