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: 55



Work Step by Step

$S_{n}=\dfrac {n}{2}\left( 2a+\left( n-1\right) d\right) $ $a_{n}=a+\left( n-1\right) d\Rightarrow a_{1}=a+\left( 1-1\right) d=a=55$ $S_{n}=\dfrac {n}{2}\left( 2a+\left( n-1\right) d\right) =\dfrac {10}{2}\left( 2\times 55+\left( 10-1\right) \times 12\right) =1090$
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