[tex]\bf ~~~~~~~~~~~~\textit{distance between 2 points} \\\\ (\stackrel{x_1}{1}~,~\stackrel{y_1}{-7})\qquad \stackrel{center}{(\stackrel{x_2}{-6}~,~\stackrel{y_2}{-4})}\qquad \qquad d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2} \\\\\\ \stackrel{radius}{r}=\sqrt{[-6-1]^2+[-4-(-7)]^2}\implies r=\sqrt{(-6-1)^2+(-4+7)^2} \\\\\\ r=\sqrt{(-7)^2+3^2}\implies r=\sqrt{58} \\\\[-0.35em] ~\dotfill[/tex]
[tex]\bf \textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~(\stackrel{-6}{ h},\stackrel{-4}{ k})\qquad \qquad radius=\stackrel{\sqrt{58}}{ r}\\[2em] [x-(-6)]^2+[y-(-4)]^2=(\sqrt{58})^2\implies (x+6)^2+(y+4)^2=56[/tex]
