SOLUTION: The function y=-5t^2+20t+2 gives the approximate height, h metres, of a thrown football as a function of time, t seconds since it was thrown. The ball hit the ground before a recei

Question 1132878: The function y=-5t^2+20t+2 gives the approximate height, h metres, of a thrown football as a function of time, t seconds since it was thrown. The ball hit the ground before a receiver get near it.
a) From what height was the football thrown?
b) How long was the ball in the air, to the nearest tenth of a second?
c) For how many seconds was the height of the ball less than 17m?
Thanks
Answer by ikleyn(52781) (Show Source): You can put this solution on YOUR website!
.

(a)  Substitute t= 0 into the right side expression and calculate.

     What you will get, is clear even without calculation.

     It is the constant term value of 2 meters.



(b)  Solve the quadratic equation  -5t^2 + 20t + 2 = 0 and use its positive root as your answer.

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