So I've got a general solution to a differential equation:

y = x/4 (ln x + D)^2

and I'm to solve it for the general initial value problem: y(x0) = y0, x>0, y>0

I then solved the equation for D, getting two results:

D = -ln (x0) + 2(y0/x0)^(1/2)

and

D = -ln (x0) - 2(y0/x0)^(1/2)

My problem now is that I have no idea how to pick one solution for D over the other. Both fit all restrictions as far as I can tell. Is it possible that both are valid and that I would need further restrictions to choose one of them?