（x²-x+y）^5的展开式中x³y²项的系数等于

(x^2-x+y)^5 =(x^2-x)^5 +5(x^2-x)^4.y + 10(x^2-x)^3.y^2 +10(x^2-x)^2.y^3 +5(x^2-x).y^4 + y^5 coef. x^3.y^2 of "(x^2-x+y)^5" =coef. x^3.y^2 of "10(x^2-x)^3.y^2" =coef. x^3.y^2 of "10x^3. (x-1)^3.y^2" =-10