1、已知x^2+y^2-2x+4y+5=0,求4/(y+1/x)的值.2、已知x=1-a/1+a,y=3-2a/2-3a,用含x的代数式表示y.要求写出明细.

已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 (3x-2y)(4x-5y)-11(x+y)(x-y)+5xy,已知X=3又1/2,y=2又1/3 已知x²+y²+5=2x+4y,求代数式（2x²-（x+y)(x-y))x((x+y-1)(x-y+1)+(1-2y)) 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(x+2009y)的值. 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(x+2009y)的值. 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值 已知((x+y)平方-(x-y)的平方-2y(x+2分之1y))除以4y=1 已知x^2+y^2-4x+2y+5=0则x^y=? 已知x^2+4x+y^2+2y+5=0,则x^y= 已知 x-2y=-2 求(2y-x)平方-2x+4y-1 已知x-y+2>=0,x+y-4>=4,2x-y-5 已知4x^2+y^2-4x+4y+5=0,求x,y