x^2+y^2-2x+4y+5
=(x^2-2x+1)+(y^2+4y+4)
=(x-1)^2+(y+2)^2>=0
当且仅渗磨当x-1=0和y+2=0同时成立时等号成立
因态喊毕帆芹此x=1,y=-2
x^2+y^2-2x+4y+5=0
x^2-2x+1+y^2+4y+4 = 0
(x-2)^2 + (y+2)^2 = 0
依据橘卖平方必定大于等于0,圆羡逗有
x-2 = 0===>派塌 x= 2
y+2= 0 ===> y= -2
x^2+y^2-2x+4y+5=0
x^2-2x+1+y^2+4y+4=0
(x-1)^2+(y+2)^2=0
x=1,y=-2
x=1
y=2