x²+y²-2x+2my+2m²-6m+9=0
x²-2x+1+y²+2my+m²+m²-6m+9-1=0
(x-1)²+(y+m)²+m²-6m+8=0
(x-1)²+(y+m)²=-(m²-6m+8)
(x-1)²+(y+m)²=-(m²-6m+9)+1
(x-1)²+(y+m)²=1-(m-3)²
1-(m-3)²>=0
(m-3)²-1