a) v = 128 ho = o (ground level)
h(t) = - 5t2 + 128t
b) h(t) will be zero when rocket hits the ground
0 = -5t^2 + 128t solve for t
c) 112 = -5t^2 + 128 t use quadratic formula to solve for t 's subtract smaller from larger value to find answer
d) maximum height will occcur at t = - b/2a where b = 128 and a = -5
e) use this value of 't' to calculate the maximum height