x+y=5000 x÷600+y÷200=15

[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y 数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y 已知xy=-2,x-y=3,求（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y 化简求值:[(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y,其中x=二分之一,y=2 先化简,再求值[(2x+y)^2-(2x+y)(2x-y)-y(5x+y)]÷(1/2y),其中x-y=2 {(x+2y)(x-2y)+[2(x-y)]²｝÷6x=? y+z÷x=Z+X÷y=X+Y÷z,X+Y+Z不等0求X+Y-Z÷X+Y+z值 当x=2013,y=2014时,代数式(x/y-y/x)÷x-y/x的值为 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 先化简,再求值 （1）[(x-y)的平方+（x+y)(x-y)]÷2x 其中X=2010,y=2009 （2)y(x+y 化简后求值 [(x-2y)²+(x-2y)(x-2y)-2x(2x-y)]÷2x 其中x=2 y=3