A model rocket is launched vertically from a platform 64 feet above the ground. The height the rocket reaches during the flight
is modeled by the equation s(t) = -16t2 48t 64, where s is the height of the rocket and t is the time in seconds since the launch. After how many seconds will the rocket hit the ground?
At ground level, the height is = 0. Therefore, s(t) = 0. 0 = -16t2 + 48t + 64 Divide both sides by -16. 0 = -16 (t2 - 3t - 4) We are left with this equation: 0 = t2 - 3t - 4 Factor out. 0 = (t - 4) (t+1) We solve each separately. 0 = (t-4) t = 4 0 = (t+1) t = -1 We are left with two answers but time cannot be negative so t = 4 seconds.
