Question

1)\(\dfrac{1}{2-\sqrt{6}}\)-\(\dfrac{1}{2+\sqrt{6}}\)

3)\(\)\(\sqrt{27a}.\sqrt{3a}\left(a>0\right)\)

rút gọn 

Answer 1

1. \(\dfrac{1}{2-\sqrt{6}}-\dfrac{1}{2+\sqrt{6}}=\dfrac{2+\sqrt{6}-2+\sqrt{6}}{4-6}=\dfrac{2\sqrt{6}}{-2}=-\sqrt{6}\)

2. \(\sqrt{27a}.\sqrt{3a}=\sqrt{81a^2}=9a\left(a>0\right)\)

Answer 2

1: \(\dfrac{1}{2-\sqrt{6}}-\dfrac{1}{2+\sqrt{6}}\)

\(=\dfrac{2+\sqrt{6}-2+\sqrt{6}}{-2}\)

\(=\dfrac{2\sqrt{6}}{-2}=-\sqrt{6}\)

3: \(\sqrt{27a}\cdot\sqrt{3a}=\sqrt{81a^2}=9a\)