The equation of a cricle is [tex](x-h)^{2}+(y-k)^{2}=r^{2}[/tex] h being the x coordinate of the given point and k being the y coordinate of the given point (r also being the radius).
Now we have to plug the points into the equation [tex](x--3)^{2} +(y-5)^{2} = 6^{2}[/tex] now just simplify the the equation [tex](x+3)^{2} +(y-5)^{2} = 36[/tex]