1/4x^2+1/3xy+1/9y^2.因式分解

x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2) 已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY 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 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² 计算3xy[2xy-x(y-2)+x-1] .化简（x-2xy）^2乘x-（9xy^3-12x^4y^2）除3xy-（2xy）^2乖x其中x=2.y=1 若x-y=4,xy=-1求(-2xy+3x+4y）-（3xy+9y-2x)的值 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) [(-3xy)^2*x^3-2x^2*(3xy^2)^3*2/1y]/9x^4*y^2 1.已知x+y=-4,xy=3,求5（2分之1xy+2y）+[6x-(2xy+y-3x)]的值2.已知（x+3）^2+|x-y+10|=0求代数式5x^2y-[2x^2y-(3xy-xy^2)-3x^2]-2xy^2-y^2的值 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