Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 11 - Section 11.4 - Partial Sums of Arithmetic and Geometric Sequences - Exercise Set - Page 659: 29

Answer

$S_{20}=-\dfrac{75}{2}$

Work Step by Step

Using $S_{n}=\dfrac{n}{2}(2a_1+(n-1)d)$, the sum of the first $ 20 $ terms of the sequence $ \dfrac{1}{2},\dfrac{1}{4},0,...,-\dfrac{17}{4} $ is \begin{array}{l} S_{20}=\dfrac{20}{2}\left(2\cdot\dfrac{1}{2}+(20-1)\left(-\dfrac{1}{4}\right)\right)\\\\ S_{20}=10\left(1-\dfrac{19}{4}\right)\\\\ S_{20}=-\dfrac{75}{2} .\end{array}
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.