Cho

Câu hỏi: Cho ${\log }_{a}x=p; {\log }_{b}x=q;$${\log }_{abc}x=r$. Hãy tính ${\log }_{c}x$ theo p, q, r

A. ${\log }_{c}x=\frac{1}{r}-\frac{1}{p}-\frac{1}{q}$

B. ${\log }_{c}x=\frac{1}{\frac{1}{r}+\frac{1}{p}+\frac{1}{q}}$

C. ${\log }_{c}x=\frac{1}{\frac{1}{r}-\frac{1}{p}-\frac{1}{q}}$

D. ${\log }_{c}x=\frac{1}{r}+\frac{1}{p}+\frac{1}{q}$