[tex]C(x_C,y_C)=C(1,3)\\ r=4\ u.c.[/tex]
[tex]\boxed{(x-x_C)^2+(y-y_C)^2=r^2}\ \therefore[/tex]
[tex](x-1)^2+(y-3)^2=4^2\ \therefore\ \boxed{(x-1)^2+(y-3)^2=16}\ \therefore[/tex]
[tex]x^2-2x+1+y^2-6y+9=16\ \therefore[/tex]
[tex]\boxed{x^2+y^2-2x-6y-6=0}[/tex]
