`B=x^2+y^2 -2x+4y+2010
`B= x^2 -2x +y^2 +4y +20210`
`B=x^2-2.x.1+1^2 -1^2 +y^2 +2y.2 +2^2 -2^2+2010`
`B= (x^2 -2x+1)+(y^2 + 4y+4) - 1 -4 +20210`
`B= (x-1)^2 +(y+2)^2 +2005`
`=>`\(MinA\) xảy ra khi `B=2005`
khi đó \(\left\{{}\begin{matrix}\left(x-1\right)^2=0\\\left(y+2\right)^2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\x=-2\end{matrix}\right.\)