SOLUTION: a ball is thrown vertically upward from the ground. its distance in feet from the ground in t seconds is s=-16t^2+96t. after how many seconds will the ball be 128 feet from the gro

Question 605201: a ball is thrown vertically upward from the ground. its distance in feet from the ground in t seconds is s=-16t^2+96t. after how many seconds will the ball be 128 feet from the ground
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
a ball is thrown vertically upward from the ground. its distance in feet from the ground in t seconds is s=-16t^2+96t. after how many seconds will the ball be 128 feet from the ground
.
Set s to 128 and solve for t:
s=-16t^2+96t
128=-16t^2+96t
dividing both sides by -16:
-8 = t^2-6t
0 = t^2-6t+8
factoring:
0 = (t-2)(t-4)
t = {2,4}
.
answer:
the ball is 128 feet from the ground at
2 seconds and again at 4 seconds
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