[tex]\bf \textit{equation of a circle}\\\\
(x-{{ h}})^2+(y-{{ k}})^2={{ r}}^2
\qquad
center~~(\stackrel{}{{{ h}}},\stackrel{}{{{ k}}})\qquad \qquad
radius=\stackrel{}{{{ r}}}\\\\
-------------------------------\\\\
(x-5)^2+(y+3)^2=16\implies [x-\stackrel{h}{5}]^2+[y-(\stackrel{k}{-3})]^2=\stackrel{r~~2}{4}[/tex]
