the formula for the equation of a circle is
[tex](x-h) ^{2} + (y-k) ^{2} =r ^{2} [/tex]
The center (h,k) and the radius (r).
In this case the center is (2,4) so you would substitute -(h,k) with 2 and 4:
[tex](x-2) ^{2} +(y-4) ^{2} =r ^{2} [/tex]
Then just substitute for r with 6:
[tex](x-2) ^{2} + (y-4) ^{2} =6 ^{2} [/tex]
and there you go!
