Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 10 - Section 10.2 - Arithmetic Sequences - Exercise Set - Page 1059: 48


First three terms : $4,2,0$ ; Last Term :$-74$ and Sum $-1400$

Work Step by Step

Here, $a_n=-2i+6$ Plug $i=1,2,3$, in the given equation. Then we have the first three terms are: $4,2,0$ Last term : $a_{40}=-2(40)+6 =-74$ The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$ or, $S_{40}=\dfrac{40}{2}[4+(-74)]=-1400$ Hence, First three terms : $4,2,0$ ; Last Term :$-74$ and Sum $-1400$
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