｛5x+2y=18,y=－x

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 x-y / 5y= (y-x)^2 / ( ) 解方程组:2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66 解方程组：2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? [x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*