Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 14 - Sequences, Series, and the Binomial Theorem - 14.3 Geometric Sequences and Series - 14.3 Exercise Set - Page 912: 50

Answer

Yes, the given infinite geometry series has a limit, and the value of the limit is ${{S}_{\infty }}=-4$.

Work Step by Step

The infinite geometry series is: $-6+3-\frac{3}{2}+\frac{3}{4}-\cdots $ Here ${{a}_{1}}=-6,{{a}_{2}}=3$ The value of $\left| r \right|$ is, $\begin{align} & \left| r \right|=\left| \frac{{{a}_{2}}}{{{a}_{1}}} \right| \\ & =\left| \frac{3}{-6} \right| \\ & =\left| -\frac{1}{2} \right| \\ & =\frac{1}{2} \end{align}$ Now, find the limit of the infinite geometry series ${{S}_{\infty }}=\frac{{{a}_{1}}}{1-r}$. $\begin{align} & {{S}_{\infty }}=\frac{{{a}_{1}}}{1-r} \\ & =\frac{-6}{1-\left( -\frac{1}{2} \right)} \\ & =\frac{-6}{1+\frac{1}{2}} \\ & =\frac{-6}{\frac{3}{2}} \end{align}$ This implies, $\begin{align} & {{S}_{\infty }}=-6\cdot \frac{2}{3} \\ & =-2\cdot 2 \\ & =-4 \end{align}$ Thus, the limit of the infinite geometric series is ${{S}_{\infty }}=-4$.
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