SOLUTION: Can someone help me? A projectile is fired straight upward from the ground level with an initial velocity of 128 feet per second. During which interval of time will the projectile

An equation for the height as a function of time is

h(t) = -16t^2 + 128t.

To answer the question, you should solve an inequality


h(t) > 128,   or   -16t^2 + 128t > 128.


It is equivalent to 16t^2 - 128t + 128 < 0,  or  t^2 -8t + 8 < 0.


To solve it, solve the quadratic equation t^2 -8t + 8 = 0.


 =  =  = .


Now the answer is:  at  < t <  seconds the projectile's height exceeds 128 feet.