Biết

C

- Hướng dẫn giải

Chọn C

Đặt $\left\{\begin{array}{l}u=x\\ dv=e^{2x}dx\end{array}\iff \left\{\begin{array}{l}du=dx\\ v=\frac{1}{2}{e}^{2x}\end{array}\right.\right.$

$$\begin{gathered} \Rightarrow I=\frac{1}{2}x.e^{2x}-\int \frac{1}{2}{e}^{2x}dx \\ =\frac{1}{2}x.e^{2x}-\frac{1}{4}{e}^{2x}+C \end{gathered}$$

Suy ra $\left\{\begin{array}{l}a=\frac{1}{2}\\ b=-\frac{1}{4}\end{array}\right.\Rightarrow a.b=-\frac{1}{8}$