College Algebra 7th Edition

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

Chapter 8, Sequences and Series - Section 8.3 - Geometric Sequences - 8.3 Exercises: 60

Answer

$S_5=\frac{55}{2}$

Work Step by Step

We need to find: $\sum_{k=1}^{5}8(-\frac{3}{2})^{k-1}$ We see that this is a geometric sequence with $a=8$ and $r=\frac{-3}{2}$. We know the partial sum of a geometric sequence is: $S_n=a_1\frac{1-r^n}{1-r}$ $S_5=8\frac{1-(-\frac{3}{2})^{5}}{1-(-\frac{3}{2})}=\frac{55}{2}$
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