in form
(x-h)^2+(y-k)^2=r^2
center is (h,k) and radius is r
complete the square for both
group x and y seprately
(x^2+16x)+(y^2-6y)=-12
take 1/2 of each linear coefient and square it then add positive and negative inside parentahsees
16/2=8, 8^2=64
-6/2=-3, (-3)^2=9
(x^2+16x+64-64)+(y^2-6y+9-9)=-12
complete the square
((x+4)^2-64)+((y-3)^2-9)=-12
expand
(x+4)^2-64+(y-3)^2-9=-12
add 64+9 to both sides
(x+4)^2+(y-3)^2=61
or
(x-(-4))^2+(y-3)^2=(√61)^2
center is (-4,3) and radius is √61
