x^2+xy=2 y^2+xy=7,则2（x-y)(x+y)=

已知x-y=4xy，则2x+3xy-2yx-2xy-y xy=-2,x+y=3,求代数式（4xy+12y)+[7x-(3xy+4y-x)] 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 若x+y分之xy=2,则-x+3xy-y分之3x-xy+3y=多少? （-3x^y+2xy)-( )=4x^+xy x^2+xy+x=36,y^2+xy+y=20,求x+y. {x,xy,lg(xy)}={0,|x|,y} 则log8（X^2+Y^2） 如果x^2+xy+y-14,y^@+xy+x=28,求x+y的值. 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知x=3y,试求(x-y)^2+2xy-y^2/x^2+7xy+y^2 已知xy/x+y=2,则代数式3x-5y+8y/-x+3xy-y的值 已知x-xy=8,xy-y=-9,求x+y-2xy的值