Giải các bất phương trình :
$\begin{array}{l}
1)\,\,\,\,\,{\log _3}\left( {5{x^2} + 6x + 1} \right) \le 0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(1)\\
2)\,\,\,\,{\log _{12}}\left( {6{x^2} - 48x + 54} \right) \le 2\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\\
3)\,\,\,\,{\log _{21}}\left( {{x^2} + 2x - 3} \right) \le 1\,\,\,\\
4)\,\,\,\,{\log _2}\left( {{x^2} - 4x - 5} \right) \le 4
\end{array}$