Tích phân $I=\int\limits_{1}^{3}{\frac{\ln x}{{{(1+x)}^{2}}}dx}$ bằng A. $-\frac{1}{4}\ln 3+\ln \frac{1}{2}.$ B. $-\frac{1}{4}\ln 3.$ C. $-\frac{1}{4}\ln 3-\ln \frac{3}{2}.$ D. $-\frac{1}{4}\ln 3+\ln \frac{3}{2}.$
Đáp án đúng: D Đặt $\left\{ \begin{array}{l}u=\ln x\\dv=\frac{dx}{{{(1+x)}^{2}}}\end{array} \right.=>\left\{ \begin{array}{l}du=\frac{dx}{x}\\v=-\frac{1}{1+x}\end{array} \right..$