x³ - 2x² - 5x + 6 = 0
x³ - x² - x² + x - 6x + 6 = 0
x²(x - 1) - x(x - 1) - 6(x - 1) = 0
(x - 1)(x² - x - 6) = 0
(x - 1)(x² + 2x - 3x - 6) = 0
(x - 1)[x(x + 2) - 3(x + 2)] = 0
(x - 1)(x + 2)(x - 3) = 0
x - 1 = 0 => x₁ = 1
x + 2 = 0 => x₂ = - 2
x - 3 = 0 => x₃ = 3
