[tex]x^2+y^2-6x+4y+13=0\\
x^2-6x+9+y^2+4y+4=0\\
(x-3)^2+(y+2)^2=0\\
(x-3)^2\geq0\\
(y+2)^2\geq0\\
......................\\
(x-3)^2+(y+2)^2\geq0\\
Dar:(x-3)^2+(y+2)^2=0=\ \textgreater \ \left \{ {{x-3=0} \atop {y+2=0}} \right.=\ \textgreater \ \left \{ {{x=3} \atop {y=-2}} \right. [/tex]