先化简再求植:0.5(x+y+2)＾+0.5(x-y-2)(x-y+2)-2(x+y)其中x-y=6,xy=21

先化简再求植:0.5(x+y+2)＾+0.5(x-y-2)(x-y+2)-2(x+y)其中x-y=6,xy=21 （x+2y-3y)- (-2x-y+xy ) 其中x+y=0.5 xy等于-0.5 [x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013 x+y)(x-y)+(x-y)^2-(6x^2y-2xy^2)/2y,其中x=-2,y=1/3 先化简,再求值(x-y/x+y)^2÷(y-x/x^2+2xy+y^2)^2*1/x+y,其中x=-4,y=1 已知xy=-2,x-y=3,求（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 先化简,再求值：（x+y)(x-y)+(x-y)^2-(x^2-3xy),其中x=2,y=0.5 化简求值：(x+y)(x-y)+(x-y)²-(6x²y-2xy²)÷2y,其中x=-2, 1.先化简,再求值:(2X+Y)^2-(2X-Y)(X+Y)-2(X-2Y)(X+2Y),其中X=0.5,Y=-2 因式分解：x×x-xy-2y×y-x-y 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y²