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At time t=0, a ball is thrown downward at 24 feet per second from a height of \(180\) feet above the ground. The equation $h = -16t^2 - 24t +180$ describes the height (in feet) of the ball. In how many seconds will the ball hit the ground? Express your answer as a decimal.

 Feb 6, 2022
 #1
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The answer is t = 3.6.

 Feb 6, 2022
 #2
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When the ball hits the ground  ,  h = 0

 

=  -16t^2 - 24 t + 180

 

Use Quadratic Formula with  a = -16    b  = -24    c = 180

\(t = {-(-24) \pm \sqrt{(-24)^2-4(-16)(180)} \over 2(-16)}\)

 

 

to calculate 't'    (Hint: it is NOT 3.6 sec )   ==== throw out the negative 't' value

 Feb 7, 2022

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