For a model rocket, the altitude h in meters, as a function of time t, in seconds, is given by h=68t-8t^2. after how many seconds will it hit the ground?

Answer 1

When it is at ground level, h(t)=0.

So solve for h(t)=0,
h(0)=68t-8t^2
=t(68-8t)=0
t=0 or t=68/8=17/4=4.25