12) (3-y)²-x-(3-y) =

12) (3-y)² - x · (3-y) = (3-y)(3-y-x)

Выносим общий множитель (3-y) за скобки:

(3-y)² - x · (3-y) = (3-y)(3-y-x)

Ответ: (3-y)(3-y-x)