H=-16t^2 +90t

Question

How long did it take the ball to hit the ground

 

Answer 1

Britney, hitting the ground is like hitting the x-axis, where y = 0

 

0 = -16t² + 90t

0 = -2t(8t - 45)

 

-2t = 0

   t = 0. We know this because this is the launching.

 

8t - 45 = 0

       8t = 45

         t = 45/8 = 5 5/8

 

Hope this helps!