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:
$S_n=\frac{n}{2}(a_1+a_n)$
$S_{12}=\frac{12}{2}(a_1+a_{12})$
$S_{12}=6(25+14)=39*6=234$
College Algebra 7th Edition
by Stewart, James; Redlin, Lothar; Watson, Saleem
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 - Page 608: 72
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