Bonjour,
(a + b)(c + d) = ac + ad + bc + bd
A = (x + 3)(x + 2)
= (x² + 2x + 3x + 6)
= x² + 5x + 6
B = (x + 3)(2x + 4)
= (2x² + 4x + 6x + 12)
= 2x² + 10x + 12
C = (x - 7)(x + 9)
= (x² + 9x - 7x - 63)
= x² + 2x - 63
D = (x - 3)(4 - x)
= 4x - x² - 12 + 3x
= 7x - x² - 12
Tu essaies les deux autres ? :)