(-4x^4y+7/2x^2y-2xy)/(-2/1xy)+(-2x)^3

因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 计算:2xy/(x+y)².(x+y)/4y x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2 (x^-4y^)/(x^+2xy+y^)/(x+2y)/(2x^+2xy) 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 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) 2x(x-y)+4xy(y-x) 因式分解2x(x-y)+4xy(y-x) 因式分解 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? (x^2+2xy+y^2-4xy)*(x^2-2xy+y^2+4xy) 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] 因式分解x^2(x-y)-4xy(x-y)-4y^2(y-x) 计算:4xy-(x+y)^2/xy(x+y)(x-y)÷x^2+xy-2y^2/x^2y+2xy^2 化简2(x²y+xy)-3(x²y-xy)-4x²y 已知1/x-1/y=2,求3x+7xy-3y/2x-3xy-2y答案是1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/7 谁能帮我解释一下=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy) 是怎