Bonjour !
A = 2(7 - x)
A = 2*7 - 2*x
A = 14 - 2x
B = 5x(3x - 6)
B = 5x*3x - 6*5x
B = 15x² - 30x
C = -7(x + 4)²
C = -7(x² + 8x + 16)
C = -7*x² - 7*8x - 7*16
C = -7x² - 56x - 112
D = (x + 3)(x - 3) - 2(5x - 6)²
D = (x + 3)(x - 3) - 2(25x² - 60x + 36)
D = x² - 9 - 50x² + 120x - 72
D = -49x² - 81 + 120x
J'espère t'avoir aidé. Bon courage !
