A ball thrown vertically upward from the ground. Its distance in feet from the the ground in t seconds is s=-16t^2+128t. After how may seconds will the ball be 192 feet from the ground?

Solution:

           192 = -16t^2 + 128t

      16t^2 - 128t + 192 = 0

   t^2 - 8t + 12 = 0

   (t - 2)(t - 6) = 0

After 2 seconds the ball be 192 feet from the ground.