\(6x^2-9x-4\left(2x-3\right)=0\)
\(\Leftrightarrow3x\left(2x-3\right)-4\left(2x-3\right)=0\)
\(\Leftrightarrow\left(2x-3\right)\left(3x-4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=0\\3x-4=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=3\\3x=4\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=\dfrac{4}{3}\end{matrix}\right.\)
Vậy \(S=\left\{\dfrac{3}{2};\dfrac{4}{3}\right\}\)