6ad-8ab-12bc+9cd Пожалуйста
6ad - 8ab - 12bc + 9cd = (6ad - 8ab) - (12bc - 9cd) =
= 2a*(3d - 4b) - 3c*(4b - 3d) = 2a*(3d - 4b) + 3c*(3d - 4b) = (3d - 4b)(2a + 3c)