Question 1195857
A stone was thrown from the top of a cliff 60 meters above sea level. The height of the stone above sea level t seconds after it was released, is given by H(t) = -5t^2 + 20t + 60 meters.
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a) Find the time it takes for the stone to reach its maximum height.
The max of the quadratic is at t = -b/2a
t = -20/-10 = 2 seconds
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b) Find the maximum height above sea level reached by the stone.
H(2) = -5*4 + 20*2 + 60 = 80 meters
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c) How long did it take before the stone struck the water?
--- Poorly worded question.
How many seconds passed from launch to impact?
H(t) = -5t^2 + 20t + 60 = 0
t^2 - 4t - 12 = 0
(t-6)*(t+2) = 0
t = 6 seconds to impact --- ignore the negative solution