[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+9)^2+(y-5)^2=64\implies [x-(\stackrel{h}{-9})]^2-[y-\stackrel{k}{5}]^2=\stackrel{r}{8^2}
\\\\\\
center~~(-9~,~5)\qquad radius=8[/tex]
