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: 53



Work Step by Step

$d=-9-0=-18-(-9)=-9$. $a_n=a_1+(n-1)d$ $a_{40}=0+(40-1)(-9)$ $a_{40}=39(-9)$ $a_{40}=-351$ $S_n=\frac{n}{2}(a_1+a_n)$ $S_{40}=\frac{40}{2}(0-351)=20(-351)=-7020$
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