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