4x^2-25x+36 = (x-4) (x-a)

Найти: a

A = (4x² - 25x + 36) / (x-4) - x

a = (4x² - 25x + 36 - x (x-4)) / (x-4)

a = (4x² - 25x+36 - x² + 4x) / (x-4)

a = (3x² - 21x + 36) / (x-4)

a = 3 (x² - 7x + 12) / (x-4)

a = 3 (x-4) (x-3) / (x-4)

a = 3 (x - 3)

a = 3x - 9

вроде так