The height of a golf ball hit off a 128-foot cliff is modeled by the function h(t) = −16t^2 + 32t + 128, where h is height in feet and t is time in seconds. Find the time the golf ball takes to reach the ground.

Set h = 0, (because the ground is at zero height here) then solve the quadratic -16t^{2} + 32t + 128 = 0 for t. There will be two values, one negative and one positive. Take the positive value.