Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 12 - Section 12.1 - Sequences and Summation Notation - 12.1 Exercises - Page 851: 41

Answer

$S_{1}=\dfrac {1}{3}$ $S_{2}=\dfrac {4}{9}$ $S_{3}=\dfrac {13}{27}$ $S_{4}=\dfrac {40}{81}$ $S_{5}=\dfrac {121}{243}$ $S_{6}=\dfrac {364}{729}$

Work Step by Step

This is geometric sequence $S_{n}=\dfrac {a_{1}\left( 1-r^{n}\right) }{1-r}$ $S_{1}=\dfrac {\dfrac {1}{3}\left( 1-\left( \dfrac {1}{3}\right) ^{1}\right) }{1-\dfrac {1}{3}}=\dfrac {1}{3}$ $S_{2}=\dfrac {\dfrac {1}{3}\left( 1-\left( \dfrac {1}{3}\right) ^{2}\right) }{1-\dfrac {1}{3}}=\dfrac {4}{9}$ $S_{3}=\dfrac {\dfrac {1}{3}\left( 1-\left( \dfrac {1}{3}\right) ^{3}\right) }{1-\dfrac {1}{3}}=\dfrac {13}{27}$ $S_{4}=\dfrac {\dfrac {1}{3}\left( 1-\left( \dfrac {1}{3}\right) ^{4}\right) }{1-\dfrac {1}{3}}=\dfrac {40}{81}$ $S_{5}=\dfrac {\dfrac {1}{3}\left( 1-\left( \dfrac {1}{3}\right) ^{5}\right) }{1-\dfrac {1}{3}}=\dfrac {121}{243}$ $S_{6}=\dfrac {\dfrac {1}{3}\left( 1-\left( \dfrac {1}{3}\right) ^{6}\right) }{1-\dfrac {1}{3}}=\dfrac {364}{729}$
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