[x(x²y-xy)-y(x²-x³y)]÷3x²y[x(x²y²-xy)-y(x²-x³y)]÷3x²y

[x(x²y-xy)-y(x²-x³y)]÷3x²y[x(x²y²-xy)-y(x²-x³y)]÷3x²y
[x(x²y-xy)-y(x²-x³y)]÷3x²y
[x(x²y²-xy)-y(x²-x³y)]÷3x²y

[x(x²y-xy)-y(x²-x³y)]÷3x²y[x(x²y²-xy)-y(x²-x³y)]÷3x²y
[x(x²y-xy)-y(x²-x³y)]÷3x²y
=x^2y[(x-1)-(1-xy)]÷3x²y
=[(x-1)-(1-xy)]÷3
=(x-2+xy)/3

原式=（x^3y^2-x^2y-x^2y+x^3y^2)÷3x^2y
=(2x^3y^2-2x^2y)÷3x^2y
=2/3*xy-1/3