$\left\{\begin{matrix}x\neq 3-\sqrt{21}\text{, }&a=\frac{22-4\sqrt{21}}{3}\\x\neq \sqrt{21}+3\text{, }&a=\frac{4\sqrt{21}+22}{3}\\x\in \mathrm{R}\text{, }&a>\frac{22-4\sqrt{21}}{3}\text{ and }a<\frac{4\sqrt{21}+22}{3}\\x\in \left(\frac{\sqrt{9a^{2}-132a+148}}{4}+\frac{3a}{4}-\frac{5}{2},\infty\right)\cup \left(-\infty,-\frac{\sqrt{9a^{2}-132a+148}}{4}+\frac{3a}{4}-\frac{5}{2}\right)\text{, }&a<\frac{22-4\sqrt{21}}{3}\text{ or }a>\frac{4\sqrt{21}+22}{3}\end{matrix}\right.$

$\left\{\begin{matrix}a<-\frac{2\left(3-5x-x^{2}\right)}{3\left(x-3\right)}\text{, }&x>3\\a\in \mathrm{R}\text{, }&x=3\\a>-\frac{2\left(3-5x-x^{2}\right)}{3\left(x-3\right)}\text{, }&x<3\end{matrix}\right.$