Question 252831
The height h (in feet) of a rocket as a function of the time t (in seconds) of flight is given by the following equation. Determine the times t when the rocket is on the ground. 

h=50+280t-16t^2 
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It's on the ground when h = 0.
-16t^2 + 280t + 50 = 0
*[invoke solve_quadratic_equation -16,280,50]
Ignore the negative value.
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PS  I don't know why this is called a rocket, it has no thrust.  It's a ballistic object, shot upward and goes up and back down due to gravity.