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: 61



Work Step by Step

$S_{n}=\dfrac {a_{1}+a_{n}}{2}\times n\Rightarrow a_{1}=\dfrac {2S_{n}}{n}-a_{n}\Rightarrow a_{1}=\dfrac {2\times S_{20}}{20}-a_{20}=\dfrac {2\times 1090}{20}-102=7$
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