h = 144t - 16t^2
h = 230
230 = 144t - 16t^2
-230 + 144t - 16t^2 = 0
16t^2 -144t + 230 = 0
8t^2 - 72t + 115 = 0
t = (72 +/- (5084 - 3680)^.5)/16 =(72 +/- 6(39)^.5)/16 = 4.5 +/- (3/8)(39)^.5 = 6.84 seconds & 2.16 seconds
At these two times, the rocket is at a height 230 feet above the ground.
144t - 16t^2 = 0
t(144 - 16t) = 0
144 - 16t = 0
t = 9
At 9 seconds, the rocket comes back to the ground.