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: 46

Answer

Yes, the infinite geometric series has a limit, and the limit is $48$.

Work Step by Step

The provided series is $12++9+\frac{27}{4}+\cdots $. Here, ${{a}_{1}}=12$, $n=\infty $ and $\begin{align} & r=\frac{9}{12} \\ & =\frac{3}{4} \end{align}$ Substituting ${{a}_{1}}=12$, $n=\infty $ and $r=\frac{3}{4}$ in ${{S}_{n}}=\frac{{{a}_{1}}}{1-r}$ , for any $r\ne 1$: $\begin{align} & {{S}_{\infty }}=\frac{12}{1-\frac{3}{4}} \\ & =\frac{12}{\frac{1}{4}} \\ & =\frac{12\cdot 4}{1} \\ & =48 \end{align}$ Thus, the infinite geometric series $12++9+\frac{27}{4}+\cdots $has a limit of 48.
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