At the point where the arrow hits the ground , it has no height above the ground.
We say , h=0
[tex]-4.9t^2+20.5t+2=0[/tex]We will solve the quadratic and obtain a value for t
The solution to the quadratic are t= - 0.095 and t=4.28
Since time function cannot be negative , we agree that
[tex]t=4.3\text{ }seconds[/tex]