A model rocket is launched from a height of 50 feet. the formula: h=-16t^2+70t+50 describes the rocket's height,h,in feet t seconds after it was launched. how long will it take the rocket to reach the ground.

Answer 1

when it hits the ground, h = 0
-16t^2 + 70t + 50 = 0
8t^2 - 35t - 25 = 0
(t-5)(8t + 5) = 0
t = 5 or t = -5/8, but t can't be negative

so it will hit the ground in 5 seconds.