College Algebra (10th Edition)

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

Chapter 1 - Section 1.2 - Quadratic Equations - 1.2 Assess Your Understanding - Page 103: 102

Answer

a. 3.091s, 0.990s b. 4.082s c. It does not reach 100m

Work Step by Step

$ s=-4.9t^2+20t $ $-4.9t^2+20t=15$ $-4.9t^2+20t-15=0$ $t=\frac{20+-\sqrt(20^2-4(-4.9*-15))}{2*-4.9}$ t= 3.091, 0.990 $-4.9t^2+20t=0$ $-t(4.9t-20)=0$ $4.9t-20=0$ $t=\frac{20}{4.9}$ t=0, 4.082 $-4.9t^2+20=100$ $-4.9t^2+20-100=0$ The discriminant of this equation is equal to $b^2-4ac$, If this is less than 0 then there are no solutions. $20^2-4(-4.9*-100)=-1560$ Because of this the object never reaches 100m.
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