Hãy rút gọn: \(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}\)

Câu hỏi :

Rút gọn: \(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}\)

A. \(\dfrac{\sqrt{6}}{5}\).

B. \(\dfrac{\sqrt{6}}{4}\).

C. \(\dfrac{\sqrt{6}}{3}\).

D. \(\dfrac{\sqrt{6}}{2}\).

* Đáp án

D

* Hướng dẫn giải

\(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}=\dfrac{(\sqrt 2)^2.\sqrt 3-\sqrt 6}{\sqrt{4.2}- 2}\)

\(=\dfrac{\sqrt 2.(\sqrt 2.\sqrt 3)-\sqrt 6}{2\sqrt 2 -2}\)\(=\dfrac{\sqrt2.\sqrt{6}-\sqrt 6}{2(\sqrt{2}-1)}\)

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

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