Solve the following equation for v: S = (-1/2)gt2 + vt

S = (-1/2)gt^2 + vt

S + (1/2)gt^2 = vt
vt = S + (1/2)gt^2
v = [S + (1/2)gt^2]/t , or
v = S/t + (1/2)gt

hope this helps~ :)