\(\Leftrightarrow\left|x^2-9x+14\right|>x^2-3x-4\)
Trường hợp 1: \(\left\{{}\begin{matrix}x^2-9x+14>0\\x^2-3x-4< =0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\in\left(-\infty;2\right)\cup\left(7;+\infty\right)\\-1< =x< =4\end{matrix}\right.\)
\(\Leftrightarrow x\in[-1;2)\)
Trường hợp 2:
\(\left\{{}\begin{matrix}x^2-3x-4>=0\\\left(x^2-9x+14-x^2+3x+4\right)\left(x^2-9x+14+x^2-3x-4\right)>0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(x-4\right)\left(x+1\right)>=0\\\left(-6x+18\right)\left(2x^2-12x+10\right)>0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\in[-\infty;-1)\cup[4;+\infty)\\\left(x-3\right)\left(x^2-6x+5\right)< 0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\in[-\infty;-1)\cup[4;+\infty)\\x\in[-\infty;1]\cup\left(3;5\right)\end{matrix}\right.\Leftrightarrow x\in[-\infty;-1)\cup[4;5)\)
