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 814: 24


$a_n=7(-0.6)^{n-1}$ and $a_7=0.326592$

Work Step by Step

The nth term is given by $a_n= a_1 r^{n-1}$ ...(1) Here, $a_1=7; r=\dfrac{a_2}{a_1}=\dfrac{-4.2}{7}=-0.6$ From equation (1), we have $a_n=7(-0.6)^{n-1}$ Plug in $n=7$ $a_7=7(-0.6)^{7-1}=0.326592$ Hence, $a_n=7(-0.6)^{n-1}$ and $a_7=0.326592$
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