Bonjour,
A = 12x - 36
A = 12 * x - 12 * 3
A = 12(x - 3)
B = 28x - 11x² + 5x²
B = 28x - 6x²
B = 2x(14 - 3x)
C = (3x + 7)(2x - 4) + (3x + 7)(5x + 8)
C = (3x + 7)(2x - 4 + 5x + 8)
C = (3x + 7)(7x + 4)
D = (6x + 5)(3x - 7) - (6x + 5)(5x - 7)
D = (6x + 5)(3x - 7 - 5x + 7)
D = (-2x)(6x + 5)