Precalculus (6th Edition)

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

Chapter 11 - Further Topics in Algebra - 11.2 Arithmetic Sequences and Series - 11.2 Exercises - Page 1025: 49



Work Step by Step

$a_{m}-a_{n}=\left( m-n\right) d\Rightarrow a_{4}-a_{2}=2d\Rightarrow 13-9=2d\Rightarrow d=2$ $a_{2}=a_{1}+01\Rightarrow 9=a_{1}+2\Rightarrow a_{1}=7\Rightarrow S_{10}=\dfrac {2\times a_{1}+\left( 10-1\right) d}{2}\times 10=\dfrac {2\times 7+9\times 2}{2}\times 10=160$
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