Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 12 Sequences and Series - 12.3 Analyze Geometric Sequences and Series - 12.3 Exercises - Skill Practice - Page 815: 46

Answer

$a_n=7\cdot(0.5)^{n-1}$

Work Step by Step

The nth term of a geometric series can be obtained by the following formula: $a_n=a_1\cdot r^{n-1}$, where $a_1$ is the first term and $r$ is the common ratio. Here the common ratio is $5$ and $a_1=3$. Hence here: $a_5/a_3=r^2$, thus $r=0.5$ and $a-3=a_1r^2$ thus $a_1=7$, hence $a_n=7\cdot(0.5)^{n-1}$
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