Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.3 Geometric Sequences; Geometric Series - 11.3 Assess Your Understanding - Page 845: 68

Answer

Series Converges. and $S_{\infty}=8$

Work Step by Step

The common ratio of a geometric sequence is equal to the quotient of any term and the term before it: $ \ r = \dfrac{a_n}{a_{n-1}}$ or, $r=\dfrac{a_2}{a_1}$ The sum of a convergent infinite geometric series is given by the formula: $S_{\infty}=\dfrac{a_1}{1-r}$ and a geometric series converges if $|r| \lt 1$. where $r \ =common \ ratio \ =\dfrac{3}{4}$ Since $r=|\dfrac{2}{3}|=\dfrac{2}{3} \lt 1$, so the infinite geometric series Converges. First term: $a_1=2(\dfrac{3}{4})^{1-1}=(2)(1)=2$ Next, $S_{\infty}=\dfrac{2}{1-(\dfrac{3}{4})}=\dfrac{2}{1/4}$ Therefore, the sum of the convergent infinite geometric series is: $S_{\infty}=8$
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