SOLUTION: A toy rocket is launched from a 2.8m platform in such a way that its height, h (in meters), after t seconds is given by the equation h=-4.9t^2+18.9t+2.8. How long will it take for

Question 513642: A toy rocket is launched from a 2.8m platform in such a way that its height, h (in meters), after t seconds is given by the equation h=-4.9t^2+18.9t+2.8. How long will it take for the rocket to hit the ground?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
Given:
h=-4.9t^2+18.9t+2.8
set h to zero and solve for t:
0=-4.9t^2+18.9t+2.8
applying the quadratic formula gives us:
t = {-0.143, 4}
we can throw out the negative solution (extraneous) leaving:
t = 4 seconds

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