Nếu $\displaystyle\displaystyle\int\limits_1^2f(x)\mathrm{\,d}x=5$ thì $\displaystyle\displaystyle\int\limits_2^1\pi f(x)\mathrm{\,d}x$ bằng
| $5\pi$ | |
| $\dfrac{\pi}{5}$ | |
| $-5\pi$ | |
| $-\dfrac{\pi}{5}$ |
Chọn phương án C.
$\displaystyle\int\limits_2^1\pi f(x)\mathrm{\,d}x=-\pi\displaystyle\int\limits_1^2f(x)\mathrm{\,d}x=-5\pi$.