x³ - 5x² + 5x - x = 0
x³ - 5x² + 4x = 0
x(x² - 5x + 4) = 0
x(x² - x - 4x + 4) = 0
x[(x² - x) - (4x - 4)] = 0
x[x(x - 1) - 4(x - 1)] = 0
x(x - 1)(x - 4) = 0
x = 0 hoặc x - 1 = 0 hoặc x - 4 = 0
*) x - 1 = 0
x = 1
*) x - 4 = 0
x = 4
Vậy x = 0; x = 1; x = 4