Bonjour ,
* Développement :
B = (6x+5) (4x-3) + (3x-4) (4x-3)
B = 20x² - 18x + 20x - 15 + 12x² - 9x - 16x + 12
B = 32x² - 23x - 3
* Factorisation :
B = (6x+5) (4x-3) + (3x-4) (4x-3)
B = (4x-3) [ (6x+5) + (3x-4) ]
B = (4x-3) [ 6x + 5 + 3x - 4 ]
B = (4x-3) (9x+1)