Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 11 - Review Exercises - Page 841: 52


$\displaystyle \sum_{i=1}^{5}3^{i-1}=121$

Work Step by Step

$\displaystyle \sum_{i=1}^{5}3^{i-1}=3^0+3^1+...+3^4$ $a_1=3^0=1$ $r=\frac{a_2}{a_1}=\frac{3^1}{3^0}=3$ $S_n=a_1(\frac{1-r^n}{1-r})$ $S_5=1(\frac{1-3^5}{1-3})=\frac{1-243}{-2}=121$
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