a model rocket is shot straight up from a roof the height at any time t is aproximated by the model h=-t(squared) +3t+28,where h is the height in metres and t is the time in seconds . When does the rocket hit the ground?

Answer 1

hit the ground? then h=0

0=-t^2 + 3t+28=t^2-3t-28=(t-7)(t+4)=0

t=7 seconds