Suppose a football is kicked from the ground and its height, h, in feet above the ground is given by h = -3.9t2 + 15.6t.

the time, t, represents the number of seconds after the ball is kicked. at what time does the football hit the ground?

The ball starts at ground level before being kicked, then hits the ground again at t = 4 seconds.            

Step-by-step explanation:

Given : Suppose a football is kicked from the ground and its height, h, in feet above the ground is given by .  The time, t, represents the number of seconds after the ball is kicked.

To find : At what time does the football hit the ground?

Solution :

The equation of kicked a football with height and time is given by,

We have to find at what time the ball hit the ground which means the height of ball became zero.

So, Substitute h=0 in the equation

Either t=0 or

The ball starts at ground level before being kicked, then hits the ground again at t = 4 seconds.