College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 8, Sequences and Series - Section 8.2 - Arithmetic Sequences - 8.2 Exercises: 72

Answer

234 poles

Work Step by Step

We have a sequence with: $a_1=25$ $a_2=24$ $a_3=23$ $a_n=26-n$ So: $a_{12}=26-12=14$ To find the sum, we use: $S_n=\frac{n}{2}(a_1+a_n)$ $S_{12}=\frac{12}{2}(a_1+a_{12})$ $S_{12}=6(25+14)=39*6=234$
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