已知x^2+y^2=4x则x^2-y^2的最大值是?

已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 已知f(x+y,y/x)=x^2-y^2,则f(x,y)= 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知F(X+Y,X-Y)=X^2*Y+X*Y^2,则F(X,Y)=? 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 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/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知3x-4y=0,则x^2-y^2/x^2+y^2 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-y=2 x-2y=4则x= y= 已知X^2+Y^2+16X-4Y+68=0,则X+Y=----------- 已知-x+y=3,则2(x-y)2次方-4(x-y)+6 已知x²+4x+y²-2y+5=0,则x+y= 已知|5x-y-8|+(7y-x+2)=0则4x+6y 已知y/x=2,则求代数式x+y/4x-5y的值 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知x=2003,y=2004,则(x+y)*(x^2+y^2)/(x^4-y^4)=