Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 12 - Section 12.3 - Geometric Sequences - 12.3 Exercises - Page 865: 23

Answer

The first five terms of the geometric sequence are 6, 18, 54, 162, 486. The common ratio is 3. $a_{n} = 6(3)^{n-1}$

Work Step by Step

$a_{n} = 2(3)^{n}$ is the formula we are given for the nth term of this geometric sequence. To find the first 5 terms, plug in n =1 ,2, 3... and solve. Since the resulting terms (6,18,54,162,486) are each multiplied by a common number (the common ratio) which equals 3 in this case the sequence is geometric. To express the nth term of the sequence in standard form $a_{n} = a(r)^{n-1}$ replace a with the first term and r with the common ratio: $a_{n} = 6(3)^{n-1}$
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