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: 71

Answer

$-657$

Work Step by Step

$\sum ^{12}_{i=4}\left( -5-8i\right) =\dfrac {n}{2}\times \left( a_{4}+a_{12}\right) \Rightarrow a_{4}=-5-8\times 4=-45;a_{12}=-5-8\times 12=-101\Rightarrow S=\dfrac {9\times \left( -45+\left( -101\right) \right) }{2}=-657$
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