27x^2(x+3)-12(x^2+3x)=0

$27x^2(x+3)-12(x^2+3x)=0 $

⇔ $27x^2(x+3)-12x(x+3)=0 $

⇔ $(x+3).(27x^2-12x)=0 $

⇔ $(x+3).(27x^2-12x)=0 $

⇔ $(x+3).3x(9x-4)=0$

⇔ \(\left[ \begin{array}{l}x=-3\\x=0,x=\frac{4}{9}\end{array} \right.\) 

Vậy $S=${$-3;0;\frac{4}{9}$}