Rút gọn biểu thức: \(\dfrac{3}{2}\sqrt 6+ 2\sqrt{\dfrac{2}{3}}-4\sqrt{\dfrac{3}{2}}\)

Câu hỏi :

Rút gọn biểu thức: \(\dfrac{3}{2}\sqrt 6+ 2\sqrt{\dfrac{2}{3}}-4\sqrt{\dfrac{3}{2}}\)

A. \(\dfrac{\sqrt 6}{3}\) 

B. \(\dfrac{\sqrt 6}{4}\) 

C. \(\dfrac{\sqrt 6}{5}\) 

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

* Đáp án

D

* Hướng dẫn giải

\(\dfrac{3}{2}\sqrt 6+ 2\sqrt{\dfrac{2}{3}}-4\sqrt{\dfrac{3}{2}}\)

 \(=3\dfrac{\sqrt 6}{2}+2\dfrac{\sqrt{2}}{\sqrt 3}-4\dfrac{\sqrt 3}{\sqrt 2}\)

\(=3\dfrac{\sqrt 6}{2}+2\dfrac{\sqrt 2\sqrt 3}{\sqrt 3 .\sqrt 3}-4.\dfrac{\sqrt 3 .\sqrt 2}{\sqrt 2.\sqrt 2}\)

\(=3\dfrac{\sqrt 6}{2}+2\dfrac{\sqrt 6}{3}-4\dfrac{\sqrt 6}{2}\)

\(=3\dfrac{\sqrt 6 .3}{2.3}+2\dfrac{\sqrt 6 .2}{3.2}-4\dfrac{\sqrt 6 .3}{2.3}\)

\(=9\dfrac{\sqrt 6}{6}+4\dfrac{\sqrt 6}{6}-12\dfrac{\sqrt 6}{6}\)

\(=(9+4-12)\dfrac{\sqrt 6}{6}=\dfrac{\sqrt 6}{6}\)

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