College Algrebra

Question

You fire a rocket straight up with an initial velocity of 312 ft/sec that is on a 9ft platform. To the nearest tenth of a second when does the rocket land

pls show work thank you :)

Answer 1

h(t) = -16t^2 + 312t + 9

it hits ground when h=0

-16t^2 +312t + 9 = 0

t = 312/32 + (1/32)sqr(312^2 + 4(16)(9))

t = 19.53 seconds

= 19.5 seconds rounded off to nearest tenth of a second to hit the ground