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Jorge is kicking a ball straight up into the air. The height of the ball is described by the equation h=-16t^2+20t, where h is the height of the ball and t is the time in seconds. How long will it take the ball to hit the ground?

 Mar 16, 2017
 #1
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When the ball hits the ground, it's height is 0

0 = -16t^2 + 20 t

divide through by 4

-4t^2 + 5t = 0          t(-4t+5) = 0    so t = 0 (when he kicks it)  and  5/4 sec (when it comes back down and hits the ground)

 Mar 16, 2017

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