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: 70

Answer

465

Work Step by Step

$\sum ^{15}_{j=1}\left( 5j-9\right) =5\sum ^{15}_{j=1}j-\sum ^{15}_{j=1}9=5\times \dfrac {n\left( n+1\right) }{2}-9\times n=5\times \dfrac {15\times \left( 15+1\right) }{2}-9\times 15=5\times 15\times 8-9\times 15=465$
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