Answer
$S_{18}=\dfrac{207}{2}$
Work Step by Step
Using $S_{n}=\dfrac{n}{2}(a_1+a_n)$, then
\begin{array}{l}
S_{18}=\dfrac{18}{2}\left(10+\dfrac{3}{2}\right)\\\\
S_{18}=9\left(\dfrac{23}{2}\right)\\\\
S_{18}=\dfrac{207}{2}
.\end{array}
Intermediate Algebra (6th Edition)
by Martin-Gay, Elayn
Published by
Pearson
ISBN 10:
0321785045
ISBN 13:
978-0-32178-504-6
Chapter 11 - Section 11.4 - Partial Sums of Arithmetic and Geometric Sequences - Exercise Set - Page 659: 32
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