解:∵(3x^2y+2xy+y^3)dx+(x^2+y^2)dy=0
==>(3x^2ydx+2xydx+x^2dy)+(y^3dx+y^2dy)=0
==>(3x^2ye^(3x)dx+2xye^(3x)dx+x^2e^(3x)dy)+(y^3e^(3x)dx+y^2e^(3x)dy)=0
(等式两端同乘e^(3x))
==>d(x^2ye^(3x))+d(y^3e^(3x))/3=0
==>x^2ye^(3x)+y^3e^(3x)/3=C/3 (C是积分常数)
==>3x^2y+y^3=Ce^(-3x)
∴此方程的通解是3x^2y+y^3=Ce^(-3x)。