Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 11 - 11.2 - Arithmetic Sequences and Partial Sums - 11.2 Exercises - Page 786: 47

Answer

$S_{5}=-25$

Work Step by Step

$a_1=-1$ and $a_n=a_5=-9$ $S_n=\frac{n}{2}(a_1+a_n)$ $S_{5}=\frac{5}{2}[-1+(-9)]=\frac{5}{2}(-10)=\frac{-50}{2}=-25$
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