[tex](x-{{ h}})^2+(y-{{ k}})^2={{ r}}^2
\\---------------------------\\
\qquad center\ ({{ h}},{{ k}})\qquad
radius={{ r}}
\\ \quad \\
\textit{we know the center}\implies center\ ({{ 6}},{{ 8}})
\\ \quad \\
\textit{what's the radius "r"?}
\\ \quad \\
\textit{distance between 2 points}\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
Center&({{ 6}}\quad ,&{{ 8}})\quad
% (c,d)
P&({{ 4}}\quad ,&{{ 1}})
\end{array}\qquad
% distance value
r= \sqrt{({{ x_2}}-{{ x_1}})^2 + ({{ y_2}}-{{ y_1}})^2}[/tex]
find "r", then plug it in the circle's equation
