Google
Câu hỏi: Nếu $\int\limits_{1}^{2}{f\left( x \right)}\text{d}x=3$ thì $\int\limits_{1}^{2}{\left[ \dfrac{1}{3}f\left( x \right)-2x \right]}\text{d}x$ bằng
A. $3.$
B. $2.$
C. $-1.$
D. $-2.$
A. $3.$
B. $2.$
C. $-1.$
D. $-2.$
Ta có $\int\limits_{1}^{2}{\left[ \dfrac{1}{3}f\left( x \right)-2x \right]}\text{d}x=\dfrac{1}{3}\int\limits_{1}^{2}{f\left( x \right)}\text{d}x-\int\limits_{1}^{2}{2x}\text{d}x=\dfrac{1}{3}.3-3=-2.$
Đáp án D.