Question

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

Answer 1

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)²]=y/(x²+y²)=(-2)/(1+4)=-2/5