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The equation y = -16t^2 + 28t + 144 describes the height (in feet) of a ball tossed up in the air at 28 feet per second from a height of 144 feet from the ground. In how many seconds will the ball hit the ground?

 Aug 8, 2020
 #1
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When the ball hits the ground,  h will = 0

 

0 = -16t^2 + 28t + 144      Use quadratic formula to find t    .... throw out negative t values

 

a = -16    b = 28    c = 144

 

 

\(t = {-28 \pm \sqrt{28^2-4(-16)(144)} \over 2(-16)}\)

 Aug 8, 2020
edited by ElectricPavlov  Aug 8, 2020
 #2
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Oh ok! I see, thank you!

 Aug 8, 2020

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