[x(x^2y^2-xy)-y(x^2-x^3y)]/3x^2y
=(x^3y^2-x^2y-x^2y+x^3y^2)/3x^2y
=(2x^3y^2-2x^2y)/3x^2y
=2x^3y^2/3x^2y-2x^2y/3x^2y
=(2xy-2)/3