Biết

C

- Hướng dẫn giải

Đáp án C

$$\begin{gathered} \underset{1}{\overset{2}{\int }}\frac{xdx}{(x+1)(2x+1)}=\underset{1}{\overset{2}{\int }}(\frac{-1}{2x+1}+\frac{1}{x+1})dx \\ =-\frac{1}{2}\ln (2x+1)+\ln (x+1)\left|{}_1^2=\right. \\ -\ln 2+\frac{3}{2}\ln 3-\frac{1}{2}\ln 5\Rightarrow abc=\frac{3}{4} \end{gathered}$$