Am nevoie de ajutor la acest ex

Explicație pas cu pas:
A(2,2), B(5,0), C(4, -4), D(-2, 0)
AM ⊥ BD, CN ⊥ BD,
AM = 2 u, CN = 4 u, BD = 7 u
[tex]Aria_{(ABCD)} = Aria_{(ABD)} + Aria_{(CBD)} \\ = \frac{AM \times BD}{2} + \frac{CN \times BD}{2} \\ = \frac{BD(AM + CN)}{2} = \frac{7(2 + 4)}{2} = 21 \: {u}^{2} [/tex]