Check the picture below.
[tex]~\hfill \stackrel{\textit{\large distance between 2 points}}{d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2}}~\hfill~ \\\\[-0.35em] ~\dotfill\\\\ A(\stackrel{x_1}{-5}~,~\stackrel{y_1}{2})\qquad B(\stackrel{x_2}{-1}~,~\stackrel{y_2}{6}) ~\hfill AB=\sqrt{[ -1- (-5)]^2 + [ 6- 2]^2} \\\\\\ ~\hfill \boxed{\sqrt{32}} \\\\\\ B(\stackrel{x_1}{-1}~,~\stackrel{y_1}{6})\qquad C(\stackrel{x_2}{3}~,~\stackrel{y_2}{2}) ~\hfill BC=\sqrt{[ 3- (-1)]^2 + [ 2- 6]^2} \\\\\\ ~\hfill \boxed{\sqrt{32}}[/tex]
[tex]C(\stackrel{x_1}{3}~,~\stackrel{y_1}{2})\qquad D(\stackrel{x_2}{-1}~,~\stackrel{y_2}{-2}) ~\hfill CD=\sqrt{[ -1- 3]^2 + [ -2- 2]^2} \\\\\\ ~\hfill \boxed{\sqrt{32}} \\\\\\ D(\stackrel{x_1}{-1}~,~\stackrel{y_1}{-2})\qquad A(\stackrel{x_2}{-5}~,~\stackrel{y_2}{2}) ~\hfill DA=\sqrt{[ -5- (-1)]^2 + [ 2- (-2)]^2} \\\\\\ ~\hfill \boxed{\sqrt{32}}[/tex]
[tex]~\dotfill\\\\ \sqrt{32}\implies \sqrt{16\cdot 2}\implies \sqrt{4^2\cdot 2}\implies 4\sqrt{2}\implies \stackrel{\textit{four times that much}}{4(4\sqrt{2})\implies \blacksquare~~ 16\sqrt{2} ~~\blacksquare}[/tex]
