Ta có:
(x-3)(2x-1)=(2x-1)(2x+3)
⇔ (x-3)(2x-1) - (2x-1)(2x+3) = 0
⇔ (2x-1)(x-3 - 2x-3) = 0
⇔ (2x-1)( -x-6 ) = 0
⇔ \(\left[ \begin{array}{l}2x-1=0\\-x-6=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=\frac{1}{2} \\x=-6\end{array} \right.\)
Vậy S = { $\frac{1}{2}$ , -6 }