Ta có: \(3\left(4-x\right)+2>x\left(x+3\right)\)
\(\Leftrightarrow12-3x+2-x^2-3x>0\)
\(\Leftrightarrow-x^2-6x+10>0\)
\(\Leftrightarrow x^2+6x-10< 0\)
\(\Leftrightarrow\left(x+3\right)^2< 19\)
\(\Leftrightarrow\left\{{}\begin{matrix}x+3>-\sqrt{19}\\x+3< \sqrt{19}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x>-\sqrt{19}-3\\x< \sqrt{19}-3\end{matrix}\right.\)