Đáp án:
$\begin{array}{l}\left(1+\dfrac{a-\sqrt{a}}{\sqrt{a}-1}\right)-\left(1-\dfrac{a+\sqrt{a}}{1+\sqrt{a}}\right)\\=1+\dfrac{a-\sqrt{a}}{\sqrt{a}-1}-1+\dfrac{a+\sqrt{a}}{1+\sqrt{a}}\\=\dfrac{a-\sqrt{a}}{\sqrt{a}-1}+\dfrac{a+\sqrt{a}}{1+\sqrt{a}}\\=\dfrac{\sqrt{a}(\sqrt{a}-1)}{\sqrt{a}-1}+\dfrac{\sqrt{a}(\sqrt{a}+1)}{1+\sqrt{a}}\\=\sqrt{a}+\sqrt{a}\\=2\sqrt{a}\end{array}$
