求道一元二次方程的填空题`````````````````````
问题描述：
求道一元二次方程的填空题`````````````````````
已知x^2+y^2-2x+4y+5=0,则2x+4y=?
求个解和过程``
答
(x-1)^2+(y+2)^2=0
x-1=0,y+2=0
x=1,y=-2
2x+4y=-6