Answer
$S_{8}=-36$
Work Step by Step
Using $S_n=\dfrac{n}{2}(2a_1+(n-1)d)$, the sum of $
-1,-2,-3,...,-8
$ is
\begin{array}{l}
S_{8}=\dfrac{8}{2}(2\cdot(-1)+(8-1)(-1))\\\\
S_{8}=4(-2+-7)\\\\
S_{8}=4(-9)\\\\
S_{8}=-36
.\end{array}
Intermediate Algebra (6th Edition)
by Martin-Gay, Elayn
Published by
Pearson
ISBN 10:
0321785045
ISBN 13:
978-0-32178-504-6
Chapter 11 - Section 11.4 - Partial Sums of Arithmetic and Geometric Sequences - Exercise Set - Page 658: 10
Update this answer!
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.
