Sharon kicks a ball from the ground into the air with an upward velocity of 64 feet per second. the function h = -16t2 + 64t models the height h, in feet, of the ball at time t, in seconds. when will the ball reach the ground again?

I believe the answer is 4 seconds

So you have to consider the height for this one. Since it's asking "WHEN (time) will the ball reach the GROUND (height). So since it's asking when it will hit the ground, the height 'h' will be 0, since you know, on the floor is 0 feet. Then since you have this, you can solve your question by plugging in H as 0... so

0 = -16t^2 + 64t

and what you can do from here is solve for time 't' to figure out what time the ball hits the ground after Sharon kicks it.

0= -16t^2 + 64t   bring over the -16t^2 to the other side

+16t^2 = 64t ... both 16t and 64t^2 can be divided by 16t, so

16t^2/16t = 64t/16t ***remember, the t's will cancel out

t = 4 Therefore, the time that it will take to hit the ground again is 4 seconds.