Substitution

Solve $xy'+y+y^2 = 0$, $y(1)=2$.

Solve $xy'+y +x = 0$, $y(1)=1$.

Solve $y^2y' = y^3-3x$, $y(0)=2$.

Solve $2yy' = e^{y^2-x^2} + 2x$.