Question 652686
A Little League baseball player throws a ball upward. The height h of the ball (in feet) t seconds after the ball is released is given by the quadratic equation
h = -16t2 +30t +4 
a) How long does it take the ball to reach a height of 18ft?
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Solve:
-16t^2 + 30t + 4 = 18
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-16t^2 + 30t - 14 = 0
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-8t^2 + 15t - 7 = 0
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t = [-15 +- sqrt(225 - 4*-8*-7)]/(-16)
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t = [-15 +- sqrt(29)]/-16
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t = 0.6 seconds and t = 1.274 seconds
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b) How long does it take the ball to hit the ground?
Solve: -16t^2 + 30t - 4 = 0
-8t^2 + 15t - 2 = 0
t = 1.73 seconds
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Cheers,
Stan H.
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