（-3xy^2)^2乘2xy除以（3x^2y^5）?=（9x²y^4)*2xy/（3x^2y^5）=18x^(2+1)y^(4+1)/（3x^2y^5）=6x^(3-2)y^(5-5)=6xy^0=6x（x-y)^5除以(y-x）^3?=-（y-x)^5/(y-x）^3=-（y-x)^(5-3)=-(y-x)²...