(6x^2y+9xy^2)\(3y+2x)计算

(6x^2y+9xy^2)(3y+2x)
=3xy(2x+3y)/(3y+x)
=3xy
(4mn-m^2-4n^2）（2n-m）
=-(4n²-4mn+m²)/(2n-m)
=-(2n-m)²/(2n-m)
=-(2n-m)
=m-2n
(a^2xy-2abxy+b^2xy)(a-b)
=xy(a²-2ab+b²)/(a-b)
=xy(a-b)²/(a-b)
=xy(a-b)
[(x^2+y^2)-4x^2y^2](x^2-y^2) 题目错误?
假如是[(x^2+y^2)²-4x^2y^2](x^2-y^2)
=[x^4+2x²y²+y^4-4x²y²]/(x²-y²)
=(x^4-2x²y²+y^4)/(x²-y²)
=(x²-y²)²/(x²-y²)
=x²-y²