Answer
$S_{25}=375$
Work Step by Step
$d=70-75=65-70=-5$
$a_n=a_1+(n-1)d$
$a_{25}=75+(25-1)(-5)$
$a_{25}=75+24(-5)=75-120$
$a_{25}=-45$
$S_n=\frac{n}{2}(a_1+a_n)$
$S_{25}=\frac{25}{2}(75-45)=\frac{25}{2}(30)=375$
Algebra and Trigonometry 10th Edition
by Larson, Ron
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: 54
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.
