The general solution of differential equation `\frac{dy}{dx}+x^2=x^2e^3y` is -- (i) `1-e^3y=ce^{x^3}`, (ii) `1-e^3y=ce^{-x^3}`, (iii) `(1-e^{-3}y)^2=c^2e^{2x^3}`, (iv) None of these.