Precalculus (6th Edition) Blitzer

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

Chapter 11 - Section 11.2 - Finding Limits Using Properties of Limits - Exercise Set - Page 1154: 65

Answer

The limit of a product, $\left( f\left( x \right)\cdot g\left( x \right) \right)$ is $\underset{x\to a}{\mathop{\lim }}\,\left( f\left( x \right)\cdot g\left( x \right) \right)=\underset{x\to a}{\mathop{\lim }}\,f\left( x \right)\cdot \underset{x\to a}{\mathop{\lim }}\,g\left( x \right)$.

Work Step by Step

For finding the limit of a product, first find the limit of each function in the product. Then multiply each of these limits. In other words, the limit of the product of two functions equals the product of their limits. In limit notation, If $\underset{x\to a}{\mathop{\lim }}\,f\left( x \right)=L $ and $\underset{x\to a}{\mathop{\lim }}\,g\left( x \right)=M $, then $\begin{align} & \underset{x\to a}{\mathop{\lim }}\,\left( f\left( x \right)\cdot g\left( x \right) \right)=\underset{x\to a}{\mathop{\lim }}\,f\left( x \right)\cdot \underset{x\to a}{\mathop{\lim }}\,g\left( x \right) \\ & =L\cdot M \end{align}$ For example: Let $ f\left( x \right)=x $ and $ g\left( x \right)=2$. To find the limit of the product of $ f\left( x \right)$ and $ g\left( x \right)$, $\underset{x\to 2}{\mathop{\lim }}\,\left( f\left( x \right)\cdot g\left( x \right) \right)$, $\begin{align} & \underset{x\to 2}{\mathop{\lim }}\,\left( f\left( x \right)\cdot g\left( x \right) \right)=\underset{x\to 2}{\mathop{\lim }}\,f\left( x \right)\cdot \underset{x\to 2}{\mathop{\lim }}\,g\left( x \right) \\ & =\underset{x\to 2}{\mathop{\lim }}\,x\cdot \underset{x\to 2}{\mathop{\lim }}\,2 \\ & =2\cdot 2 \\ & =4 \end{align}$
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