Calculus Concepts: An Informal Approach to the Mathematics of Change 5th Edition

Published by Brooks Cole
ISBN 10: 1-43904-957-2
ISBN 13: 978-1-43904-957-0

Chapter 1 - Ingredients of Change: Functions and Limits - 1.1 Activities - Page 10: 21

Answer

(a) $ t = 2.786$ and $ t = -4.785$ (b) $ t = -0.359$ and $ t = -4.640$

Work Step by Step

(a) Expression given: $ \frac{10}{t+5}+6t = 18$ Multiply both sides by $t+5$: $ 10+6t\times(t+5) = 18\times(t+5)$ Expand: $ 10+6t^{2}+30t = 18t + 90$ Rearrange: $ 6t^{2}+12t - 80= 0$ Solve using calculator or quadratic formula to find: $ t \approx 2.786$ and $ t \approx -4.785$ (b) Expression given: $ \frac{10}{t+5}+6t = 0$ Multiply both sides by $t+5$: $ 10+6t\times(t+5) = 0\times(t+5)$ Expand: $ 10+6t^{2}+30t = 0$ Rearrange: $ 6t^{2}+30t+10= 0$ Solve using calculator or quadratic formula to find: $ t \approx -0.359$ and $ t \approx -4.640$
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