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Câu hỏi: Cho a là số thực dương tùy ý khi đó ${{\log }_{2}}\left( \dfrac{{{a}^{5}}}{2\sqrt{2}} \right)$ bằng:
A. $5{{\log }_{2}}a-\dfrac{3}{2}$
B. $5{{\log }_{2}}a-\dfrac{2}{3}$
C. $5{{\log }_{2}}a+\dfrac{3}{2}$
D. $\dfrac{3}{2}-5{{\log }_{2}}a$
A. $5{{\log }_{2}}a-\dfrac{3}{2}$
B. $5{{\log }_{2}}a-\dfrac{2}{3}$
C. $5{{\log }_{2}}a+\dfrac{3}{2}$
D. $\dfrac{3}{2}-5{{\log }_{2}}a$
Ta có: ${{\log }_{2}}\left( \dfrac{{{a}^{5}}}{2\sqrt{2}} \right)={{\log }_{2}}\left( \dfrac{{{a}^{5}}}{{{2}^{\dfrac{3}{2}}}} \right)={{\log }_{2}}{{a}^{5}}-{{\log }_{2}}{{2}^{\dfrac{3}{2}}}=5{{\log }_{2}}a-\dfrac{3}{2}$.
Đáp án A.