Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 5 - Number Theory and the Real Number System - 5.7 Arithmetic and Geometric Sequences - Exercise Set 5.7: 36

Answer

$a_{80}=-842$

Work Step by Step

The $n^{th}$ term of an arithmetic sequence can be found using the formula: $a_n=a_1+(nāˆ’1)d$ where d = common difference $a_1$ = first term $a_n$=$n^{th}$ term The given arithmetic sequence has: $a_1=106 \\d=-12$ Use the formula above to find the 80th term: $a_n=a_1+(nāˆ’1)(d) \\a_{80}=106+(80-1)(-12) \\a_{80}=106+79(-12) \\a_{80}=106+(-948) \\a_{80}=-842$
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