Bonjour,
1)
a) AD = AF + FD = (x + 3) + (x - 2) = 2x + 1
b) aire ABCD = (2x + 1)² = 4x²+4x+1
c) aire ABEF = (x + 3)(2x + 1) = 2x²+x+6x+3 = 2x²+7x+3
d) aire ECDF = aire ABCD - aire ABEF
= 4x²+4x+1 - (2x²+7x+3)
= 2x²-3x-2
e) (x-2)(2x+1) = 2x²+x-4x-2 = 2x²-3x-2
2) si x=2
aire ABCD = (2(2)+1)² = 25 cm²
aire ABEF = (2+3)(2(2)+1) = 25 cm²
si x=2 alors aire ABCD = aire ABEF
si x=2 alors FD=x-2=0 donc AF=AD
donc aire ABCD=AD²=AF²=aire ABEF
