Khi rút gọn biểu thức
\(2\sqrt{3a}-\sqrt{75a}+a\sqrt{\dfrac{6}{5}.\dfrac{5}{2a}}-\dfrac{2}{5}\sqrt{300a^3}\) (a > 0), ta được kết quả là
\(-2\sqrt{3a}\left(1+2a\right)\). \(2\sqrt{3a}\left(1+2a\right)\). \(-2\sqrt{3a}\left(1-2a\right)\). \(-2\sqrt{3a}\). Hướng dẫn giải:\(2\sqrt{3a}-\sqrt{75a}+a\sqrt{\dfrac{6}{5}.\dfrac{5}{2a}}-\dfrac{2}{5}\sqrt{300a^3}\)
\(=2\sqrt{3a}-5\sqrt{3a}+a\sqrt{\dfrac{3}{a}}-\dfrac{2}{5}.10.a\sqrt{3a}\)
\(=-3\sqrt{3a}+\sqrt{\dfrac{3}{a}.a^2}-4a\sqrt{3a}\)
\(=-3\sqrt{3a}+\sqrt{3a}-4a\sqrt{3a}\)
\(=-2\sqrt{3a}-4a\sqrt{3a}\)
\(=-2\sqrt{3a}\left(1+2a\right)\).
