$\displaystyle \begin{array}{{>{\displaystyle}l}} Q=\left(\frac{\sqrt{a} +2}{a+4\sqrt{a} +4} +\frac{\sqrt{a} -2}{a-4}\right) .\frac{\sqrt{a} +2}{2\sqrt{a}} \ \\ Q=\left(\frac{\sqrt{a} +2}{\left(\sqrt{a} +2\right)^{2}} +\frac{\sqrt{a} -2}{\left(\sqrt{a} -2\right)\left(\sqrt{a} +2\right)}\right) .\frac{\sqrt{a} +2}{2\sqrt{a}} \ \\ Q=\left(\frac{1}{\sqrt{a} +2} +\frac{1}{\sqrt{a} +2}\right) .\frac{\sqrt{a} +2}{2\sqrt{a}} \ \\ Q=\frac{2}{\sqrt{a} +2} .\frac{\sqrt{a} +2}{2\sqrt{a}} =\frac{1}{\sqrt{a}} =\frac{\sqrt{a}}{a\ } \end{array}$
