Answer:
2.86 seconds
Step-by-step explanation:
We presume the height is measured above the ground, so the height when the ball hits the ground is 0 feet. Putting that into the equation and solving for t, we get ...
0 = 157 -9t -16t^2
We can use the quadratic formula with a=-16, b=-9, c=157 to find the solution.
t = (-b -√(b^2 -4ac))/(2a) . . . . . we are not interested in the negative solution
t = (-(-9) -√((-9)^2 -4(-16)(157)))/(2(-16))
t = (9 -√10129)/-32 = (9 -100.6429)/-32 ≈ 2.86384
The ball will hit the ground about 2.86 seconds after it is thrown.
