Question 967670: A ball is thrown into the air from the balcony of an apartment building and falls to the ground. The height, h, in metres, of the ball relative to the ground, t seconds after being thrown is given by: h=-5t^2 + 10t + 35
c)After how many seconds does the ball hit the ground?
*I know that the equation in vertex form is: h=-5(t-1)^2+40
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A ball is thrown into the air from the balcony of an apartment building and falls to the ground. The height, h, in metres, of the ball relative to the ground, t seconds after being thrown is given by: h=-5t^2 + 10t + 35
*I know that the equation in vertex form is: h=-5(t-1)^2+40
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So the vertex (top point) is (1,40)
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c)After how many seconds does the ball hit the ground?
Solve::
-5(t-1)^2 + 40 = 0
-5(t-1)^2 = -40
(t-1)^2 = 8
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t-1 = 2sqrt(2)
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Ans: t = [1+2sqrt(2)] seconds
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Cheers,
Stan H.
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