Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 11 - Further Topics in Algebra - 11.3 Geometric Sequences and Series - 11.3 Exercises: 6

Answer

$121$

Work Step by Step

$\sum ^{5}_{i=1}81\left( \dfrac {1}{3}\right) ^{i-1}=\dfrac {a_{1}\left( 1-rn\right) }{1-r}\Rightarrow a_{1}=81\left( \dfrac {1}{3}\right) ^{1-1}=81;r=\dfrac {1}{3}\Rightarrow S5\dfrac {81\left( 1-\left( \dfrac {1}{3}\right) ^{5}\right) }{1-\dfrac {1}{3}}=\dfrac {81\left( \dfrac {242}{243}\right) }{\dfrac {2}{3}}=121$
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