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Câu hỏi: Cho $\int\limits_{-1}^{2}{f\left( x \right)} \text{d}x=2$, $\int\limits_{-1}^{2}{g\left( x \right)} \text{d}x=-1$. Khi đó $\int\limits_{-1}^{2}{\left[ x+2f\left( x \right)+3g\left( x \right) \right]} \text{d}x$ bằng
A. $\dfrac{5}{2}$.
B. $\dfrac{7}{2}$.
C. $\dfrac{17}{2}$.
D. $\dfrac{11}{2}$.
A. $\dfrac{5}{2}$.
B. $\dfrac{7}{2}$.
C. $\dfrac{17}{2}$.
D. $\dfrac{11}{2}$.
Ta có $\int\limits_{-1}^{2}{\left[ x+2f\left( x \right)+3g\left( x \right) \right]} \text{d}x$ $=\int\limits_{-1}^{2}{x\text{d}x}+2\int\limits_{-1}^{2}{f\left( x \right)\text{d}x}+3\int\limits_{-1}^{2}{g\left( x \right)\text{d}x}=\dfrac{3}{2}+2.2+3.\left( -1 \right)=\dfrac{5}{2}$.
Đáp án A.