Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 8 Rational Functions - 8.6 Solve Rational Equations - 8.6 Exercises - Problem Solving - Page 594: 35


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Work Step by Step

Given: $n=\frac{635t^2-7350t+27200}{t^2-11.5t+39.4}$ Setting it equal to 720, we have: $\frac{635t^2-7350t+27200}{t^2-11.5t+39.4}=720\\635t^2-7350t+27200=720t^2-8280t+28368\\85t^2-930t+1168=0$ Solve the equation using the quadratic formula: $t=\frac{930\pm\sqrt (-930)^2-4\times85\times1168}{2\times85}\approx\frac{930\pm 683.94}{170}$ Thus, $t_1=\frac{930-683.94}{170}\approx1.45\\t_2=\frac{930+683.94}{170}\approx9.49$ Since the condition is $0\leq t\leq 9$, the only solution here is $t=1.45$. $t$ is the number of years after $1994$; hence in the year 1995 the total number of CDs shipped is about 720 million.
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