（1-x^2）(1-y^2)-4xy

(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 1.（xy-1）^2-(x+y-2xy)(2-x-y)2.(x+y)(x+y+2xy)+(xy-1)(xy+1) 分解因式：(X+Y）*（X+Y+2XY）+（XY+1）*（XY-1） XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2) 1-2/x+y=xy,4y+6x=xy.求xy的解? (x²-4y²)÷(2x+y)/xy×1/x(2y-x）(2x+y)/xy 1/x(2y-x） 都是一项 （1）3xy×(-4xy+2xy-1)（2）(x+2y)(3x-2y)+(x-2y)(3x+2y)因式分解 .(x+y-2)(x+y-2xy)+(xy-1)^2 化简 2（xy-xy²+3）-（-4xy²+xy-1） 其中,x等于--4,y等于-3 5xy^2-{2x^y-[3xy^2-（xy^2-2x^2y）]/（-1/2xy）} 化简!1、（x^2-xy）+xy+y^2 2、3（x^2-xy）-xy+y^2 计算：（1）8x^2y^2*(-3x/4y^5) (2)(x+y)^2/xy-y^2*(y-x)^2/xy+y^2 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 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 x-2xy-1+4y² (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1