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At time t=0, a ball is thrown downward at 24 feet per second from a height of 160 feet above the ground. The equation \(h = -16t^2 - 24t +160\)  describes the height (in feet) of the ball. In how many seconds will the ball hit the ground? Express your answer as a decimal.

 Jul 10, 2016
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First set h = 0, then divide each term by -8 to get:

 

2t^2 + 3t - 20 = 0. This factors as:

 

(2t - 5)(t + 4) = 0

 

The only positive solution is given by 2t - 5 = 0 or t = 5/2

 

So t = 2.5 seconds

 Jul 10, 2016

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