College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 9 - Review Exercises - Page 679: 35


See below.

Work Step by Step

b) The sum of the first $n$ terms of an arithmetic sequence can be obtained by the following formula: $\frac{n(a_1+a_n)}{2},$ where $a_1$ is the first term, $a_n$ is the nth term and $n$ is the number of terms. Hence here: $d=-1,a_1=30,a_{16}=15,n=16$ Hence here the sum: $\frac{n(a_1+a_n)}{2}=\frac{16(30+15)}{2}=360$
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