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