College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 9 - Section 9.1 - Sequences - 9.1 Assess Your Understanding - Page 648: 72

Answer

$$\require{cancel} \\\sum_{k=1}^{24}-k=-300$$

Work Step by Step

RECALL: (1) $$\sum_{i=1}^{n}k = \dfrac{n(n+1)}{2}$$ (2) $$\sum_{i=1}^{n}-k = -\sum_{k=1}^{n}k$$ Use rule (2) above to obtain: $$\sum_{k=1}^{24}(-k) = -\sum_{k=1}^{24}k$$ Use rule (1) above to obtain: $$\require{cancel} \\-\sum_{k=1}^{24}k=-\dfrac{24(25)}{2}=-300$$
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