4x^2-14xy+6y^2-7x+y-2因式分解

1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 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 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 3(x-y)²-7(x-y)+8(x-y)²+6(x-y)求详细过程（2） 5xy-4x²y-8xy²+3xy-xy²+4x²y 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) x^2-xy-2y^2+x+7y-6 x²+xy-2y²-x+7y-6 2X^+XY-Y^-4X+5Y-6 2x^+xy-y^-4x+5y-6=? x^3+x+30x^2-4xy+4y^2+7x-14y+12 4x^2-14xy+6y^2-7x+y-2因式分解 x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2 5x^3y*(-3y)^2+(-6xy)^2*(-xy)+xy^3*(-4x^2) (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 1-2/x+y=xy,4y+6x=xy.求xy的解? 先化简,再求值：-4x+7x-5-3x-6x+2,其中x=-2分之1 4xy-3x-xy先化简,再求值：-4x+7x-5-3x-6x+2,其中x=-2分之14xy-3x-xy+y+x-3xy-2y+2x+x,其中x=-5,y=-1 x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值