s'il vous plaît j'y comprend rien

Bonsoir,

A = (5x + 7)²
A = 25x² + 70x + 49

B = (4x - 3) (6x + 2)
B = 24x² + 8x - 18x - 6
B = 24x² - 10x - 6

C = (2 - 6x)²
C = 4 - 24x + 36x²
C = 36x² - 24x + 4

D = (9x - 3) (9x + 3)
D = 81x² - 9

E = (1 + 2x)²
E = 1 + 4x + 4x²
E = 4x² + 4x + 1

F = (4 - 7x) (4 + 7x)
F = 16 - 49x²
F = - 49x² + 16