dy/dx=y/(x+y^3)
dx/dy=x/y+y²
即
dx/dy-1/y ·x=y²
所以
x=e^[-∫（-1/y）dy] (∫y²e^[∫（-1/y）dy]dy+c)
=y (∫y²/y dy+c)
=y(∫ydy+c)
=y(y²/2+c)
=cy+1/2 y³