Răspuns:
[tex]AB=\sqrt{(4-1)^{2} +(5-5)^{2} } =\sqrt{9+0} =\sqrt{9} =3\\BC=\sqrt{(4-4)^{2} +(9-5)^{2} } =\sqrt{16} =4\\AC=\sqrt{(4-1)^{2} +(9-5)^{2} } =\sqrt{25} =5\\P_{ABC} =3+4+5=12\\BC=4\\BD=5\\CD=3\\P_{BCD} =12\\P_{ABC} =P_{BCD}[/tex]
Explicație pas cu pas: