（1-2X+Y）是4XY-4X^2-Y^2-M的一个因式,则M的值为?

(x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² (x²-4y²)÷(2x+y)/xy×1/x(2y-x）(2x+y)/xy 1/x(2y-x） 都是一项 已知1/x-1/y=4,求(2x+xy-2y)/(x-2xy-y)∵1/x-1/y=4∴(y-x)/xy=4∴y-x=4xy∴x-y=-4xy（y-x）/xy=4是如何求出来的,知道是通分.还有y-x=4xy x-y=-4xy又是如何求出来的? 若|x-3|+（y+2）=0,则（x-y+4xy/x-y）（x+y-4xy/x+y）的值是 若|x-3|+（y+2）²=0,则（x-y+4xy/x-y）（x+y-4xy/x+y）的值是 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 计算：（1）8x^2y^2*(-3x/4y^5) (2)(x+y)^2/xy-y^2*(y-x)^2/xy+y^2 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) 约分：（1）-4x^2y^3/10xy^4(2)（x^2-4xy+4y^2)(y-x)/(2y-x)(x^2-y^2) (1)ac分之2bc (2)xy²分之（x+y）y (3)(x+y)^2/x^2+xy (4)(x-y)^2/x^2-y^2 x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² x-y/x^2+xy除以xy-x^2/x^2y^2-x^4*1/x-y （1）3xy×(-4xy+2xy-1)（2）(x+2y)(3x-2y)+(x-2y)(3x+2y)因式分解 化简:[4xy(x-y)^-1 + (xy^-1 - x^-1y)/(x^-1 + y^-1)] / (x+y)^2 已知x-y=1,xy=2,（-2xy+2x+3y）—（3xy+2y-2x）-（x+4y+xy）?主要是过程~谢谢,告诉我解这类题的方法谢谢~ 分解因式x^2y+x^2y+2xy^2-4xy^3是x^3y+x^2y+2xy^2-4xy^3 计算:2xy/(x+y)².(x+y)/4y