[tex]BD = \sqrt{ {(x_{D}-x_{B})}^{2} +{(y_{D}-y_{B})}^{2} }[/tex]
[tex]BD = \sqrt{ {(2 - 1)}^{2} + {( - 3 - 2)}^{2} } [/tex]
[tex]BD = \sqrt{ {1}^{2} + {( - 5)}^{2} } [/tex]
[tex]BD = \sqrt{1 + 25} [/tex]
[tex]BD = \sqrt{26} [/tex]
[tex]BD=d=l\sqrt{2}[/tex]
[tex]\sqrt{26}=l\sqrt{2}[/tex]
[tex]l=\frac{\sqrt{26}}{\sqrt{2}}[/tex]
[tex]l=\sqrt{13}[/tex]
[tex]A={l}^{2}={(\sqrt{13})}^{2}=13[/tex]
