Đặt $\Large a=\log_{7}11, b=\log_{2}7$. Hãy biểu diễn $\Large \log_{\s

Đặt $\Large a=\log_{7}11, b=\log_{2}7$. Hãy biểu diễn $\Large \log_{\sqrt[3]7}\dfrac{121}{8}$ theo a và b

• A.

  A. $\Large \log_{\sqrt[3]7}\dfrac{121}{8}=6a+\dfrac{9}{b}$

• B.

  B. $\Large \log_{\sqrt[3]7}\dfrac{121}{8}=6a-\dfrac{9}{b}$

• C.

  C. $\Large \log_{\sqrt[3]7}\dfrac{121}{8}=6a-9b$

• D.

  D. $\Large \log_{\sqrt[3]7}\dfrac{121}{8}=\dfrac{2}{3}a-\dfrac{9}{b}$

Chọn B

Ta có: $\Large \log_{\sqrt[3]7}\dfrac{121}{8}=3(\log_{7}121-\log_{7}8)=6\log_{7}11-9\log_{7}2$$\Large =6.\log_{7}11-9.\dfrac{1}{\log_{2}7}=6a-\dfrac{9}{b}$