Đáp án + giải thích các bước giải:
$9(3x-2)=x(2-3x)\\\to 9(3x-2)-x(2-3x)=0\\\to 9(3x-2)+x(3x-2)=0\\\to (9+x)(3x-2)=0 \\\to \left[ \begin{array}{l}9+x=0\\3x-2=0\end{array} \right.\\\to \left[ \begin{array}{l}x=-9\\3x=2\end{array} \right.\\\to \left[ \begin{array}{l}x=-9\\x=\dfrac{2}{3}\end{array} \right.$
Vậy $S={-9;\dfrac{2}{3}}$