已知x^2+y^2-2x+4y+5=0.求{(x^4-y^4)/[(x+y)(2x-y)]}*{[(2x-y)/(xy-y^2)]}/{[x^2+

由题得：(x-1)²+(y+2)²=0所以,x=1,y=-2{(x^4-y^4)/[(x+y)(2x-y)]}*{[(2x-y)/(xy-y^2)]}/{[x^2+y^2]/y}^2={[(x-y)(x+y)(x²+y²)]/[(x+y)(2x-y)]}*[(2x-y)/(x-y)y]*[y²/(x²+y²)...