Explications étape par étape:
A = (2a + 3)²
B = (3a - 2)²
D = (a + 2 + 4)(a + 2 - 4) = (a + 6)(a - 2)
E = (6 + 2a - 3)(6 - 2a + 3) = 2a + 3)(-2a + 9)
C = (6 - a)²
F = (4/5 + 4/9a - 5) (4/5 - 4/9a + 5)
= (4/9a + 4/5 - 25/5 )(- 4/9a + 4/5 + 25/5)
= (4/9a - 21/5) (-4/9a + 29/5)