Convert the given equation into the form  (x-h)^{2}  (y-k)^{2}  r^{2}   where the center is (h,k) and r is the radius

in order to achieve this, use completing the square on the y value, the formula is (b/a)^2

so, youll have  (x)^{2}  (y)^{2} -8y + 16= 0+9 +16 
add sixteen to the other side too so that you will not violate the equality law
then use factoring, youll get
(x)^{2} [/tex] +  (y-4)^{2} = 25

so, (0,4) as center and 5 as radius