( x- 1 ) mũ 3 - ( x + 3 ) mũ 3 +28= 0

`(x - 1)^3 - (x + 3)^3 + 28 = 0`

`=>x^3 - 3x^2 + 3x - 1 - (x^3 + 9x^2 + 27x + 27) + 28 = 0`

`<=>x^3 - 3x^2 + 3x - 1 - x^3 - 9x^2 - 27x - 27 + 28 = 0`

`<=>-12x^2 - 24 = 0`

`<=>-12x(x + 2) = 0`

`<=>`$\left[\begin{matrix} -12x = 0\\ x + 2 = 0\end{matrix}\right.$

`<=>`$\left[\begin{matrix} x = 0\\ x = -2\end{matrix}\right.$

Vậy: `x = 0` hay `x = -2`