Svp ! aider moi le 2,3 merci ! :)

2) Aire de 1 = CF² = (CB-BF)² =(a-b)²
Aire de 2 = EB x BF = (a-b)b
Aire de 3 = AE x AD = (DC-GC)a = (a-(a-b))a=ba

3) 1+2+3=(a-b)²+(a-b)b+ba=a²-2ab+b²+ab-b²+ba=a²-2ab+2ab+b²-b²=a²=Aire ABCD