[tex]\bf \textit{distance between 2 points}\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
&({{ -7}}\quad ,&{{ 5}})\quad
% (c,d)
&({{ 4}}\quad ,&{{ 1}})
\end{array}\qquad
% distance value
d = \sqrt{({{ 4}}-{{ (-7)}})^2 + ({{ 1}}-{{ 5}})^2}
\\\\\\
d=\sqrt{(4+7)^2+(1-5)^2}[/tex]
