207x^3y^3 -12x^5 -27xy ^4

x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2 xy=-2,x+y=3,求代数式（4xy+12y)+[7x-(3xy+4y-x)] [-(x-y)^2/xy]^-4*(y^2-xy/x)^3*(x^4/y^10)÷(xy-y^2/x)^-5=-y(y- 5xy^2-[3xy^2-(4xy^2-2x^y)]+x^2y-xy^2如何化简 -3(xy-2x²)-[y²-(5xy-4x²)+2xy] 因式分解 求过程 x-xy+3y-3x 2x+xy-y-4x+5y-6 （-3x^y+2xy)-( )=4x^+xy 先化简,再求值：[-xy/(x-y)^2]^4*(x^2-xy/x)3*x^4/y^10÷(x/xy-y^2)^5 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) x^8-x^7y+x^6y^2-x^5y^3+x^4y^4-x^3y^5+x^2y^-xy^7+y^8 (4x^2y-5xy^2)-(3x^3y-4xy^2) x*-2xy+3y*=9 4x*-5xy+6y*=30