`4(3x-2) +(2-3x)^3 = 0`

`<=> -4(2-3x) + (2-3x)^3 =0`

`<=> (2-3x)[-4 +(2-3x)^2]=0`

`<=>(2-3x)(-4 +9x^2-12x+4)=0`

`<=>(2-3x)(9x^2-12x)=0`

`<=>(2-3x) . 3x(3x - 4)=0`

`<=>` $\left[\begin{matrix} 2-3x=0\\ 3x=0 \\ 3x-4=0\end{matrix}\right.$

`<=>` $\left[\begin{matrix} x=\dfrac{2}{3}\\ x=0 \\x=\dfrac{4}{3}\end{matrix}\right.$

Vậy `S={2/3 ;0 ;4/3}`