Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 10 - Review Exercises - Page 1125: 42



Work Step by Step

The general formula to find the sum of a finite geometric sequence is given as: $ S_{n}=\dfrac{a_1(1-r^n)}{1-r}$ Here, $ a_1=8$ and $ r=\dfrac{1}{2}$ Plug $ n=15$ $ S_{n}=\dfrac{a_1(1-r^n)}{1-r}$ Now, $ S_{7}=\dfrac{8 \times [1-(\dfrac{1}{2}]^7)}{1-(\dfrac{1}{2})}=\frac{127}{8}=15.875$
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