3х³ - 27х = 0
3х(x² - 9) = 0
3х(x² - 3²) = 0
3х(x - 3)(x+3) = 0
x₁ = 0
x - 3 = 0 => x₂ = 3
x + 3 = 0 => x₃ = - 3
ответ: {- 3; 0; 3}
