Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 11 - Section 11.2 - Arithmetic Sequences - Exercise Set - Page 841: 70



Work Step by Step

Sum of the an arithmetic series can be calculated by using formula $S_n=\dfrac{n}{2}(2a_1+(n-1)d)$ Our aim is to determine a formula for the general term of the arithmetic sequence $a_n$. Such as: $a_n=a_1+(n-1)d$ For $n=26$ $s_{26}=13(a_1+a_{26})$ ...(1) Now, $a_n=a_1+(n-1)d$ $\implies a_{26}=a_1+(25)(2)=80$ From equation (1), we have $s_{26}=13(30+80)=1430$
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