a)ĐKXĐ:[tex]a> 1[/tex]
[tex]K=\left ( \frac{\sqrt{a}}{\sqrt{a}-1}-\frac{1}{a-\sqrt{a}} \right ):\left ( \frac{1}{\sqrt{a}+1}+\frac{2}{a-1} \right )\Leftrightarrow K=\left [ \frac{\sqrt{a}}{\sqrt{a}-1}-\frac{1}{\sqrt{a}\left ( \sqrt{a}-1 \right )} \right ]:\left ( \frac{1}{\sqrt{a}+1}+\frac{2}{a-1} \right )[/tex]