This problem relates to projectiles without air resistance, but using DEs Solve the IVP to find an expression for v(t) in terms of g and t(no m dependence)

1st: Given mv'(t)=-mg ; v(0)=v0

2nd: v'(t)=-g (dividing by m, since there is no mass dependence)

3rd: integrate v(t)=-9.8t

I'm stuck here, because I am to use the result from v(t) and solve for the IVP: x'(t)=v(t) ; x(0)=0 (height above ground of the projectile) in terms of v0,g, and t.