Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 6 - Exponential Functions and Sequences - 6.7 - Recursively Defined Sequences - Exercises - Page 344: 14

Answer

A recursive rule for the sequence is $a_1=8,a_n=3a_{n-1}$

Work Step by Step

The given sequence from the table is $8,24,72,216,...$ The first term is $a_1=8$. Calculate ratio between each pair of consecutive terms. $\frac{24}{8}=3$ $\frac{72}{24}=3$ $\frac{216}{72}=3$ The common ratio is $d=3$. So, the sequence is geometric. Recursive equation for a geometric sequence. $a_n=r\cdot a_{n-1}$ Substitute $3$ for $r$. $a_n=3a_{n-1}$ Hence, a recursive rule for the sequence is $a_1=8,a_n=3a_{n-1}$
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