Step-by-step explanation:
x³ - 23x² + 142x - 120
x³ - x² - 22x² + 22x + 120x - 120
x²(x - 1) - 22x(x - 1) + 120(x - 1)
(x - 1)(x² - 22x + 120)
(x - 1)(x² - 10x - 12x + 120)
(x - 1)[x(x - 10) - 12(x - 10)]
(x - 1) (x - 10) (x - 12)
