Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 12 - Section 12.2 - Arithmetic Sequences - 12.2 Exercises - Page 857: 36


$d=-15$ $a_{n}=79-15n$ $ a_{5}=4$ $a_{100}=-1421$

Work Step by Step

$d=a_{n+1}-a_{n}=19-34=34-49=49-64=-15$ $a_{n}=a+\left( n-1\right) d\Rightarrow a_{1}=a+\left( 1-1\right) d=a=64$ $a_{n}=a+\left( n-1\right) d=64+\left( n-1\right) \times \left( -15\right) =64-15n+15=79-15n$ $a_{n}=79-15n\Rightarrow a_{5}=79-15\times 5=4;a_{100}=79-15\times 100=-1421$
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