x^2+4y^2=4xy.求x+2y/x-y

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/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 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*y)的值 当x-y=2xy时,求4x-3xy-4y/xy 1-2/x+y=xy,4y+6x=xy.求xy的解? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 已知x-y=4xy,求2x+3xy-2y/x-2xy-y的值 x-y=4xy,试求2x+3xy-2y/x-2xy-y 已知x-y=4xy,求x-2xy-y分之2x+3xy-2y的值! x-y=4xy,试求2x+3xy-2y/x-2xy-y 诺x+y=6,xy=4 求(5x-4y-3xy)-(8x-y+2xy) 已知X+Y=2XY,求4X-5XY+4Y 除以X+XY+Y 的值 已知X+Y=2XY,求4X-5XY+4Y 除以X+XY+Y 的值 已知x+y=2xy,求4x-5xy+4y/xy-x-y的值 已知x-y=3xy,求5x+2xy-5y/x-4xy-y的值 x^2+4y^2=4xy.求x+2y/x-y 求 f(x,y)=x^4+y^4-x^2-y^2-xy的极值!