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Câu hỏi: Nếu $\int\limits_{1}^{2}{f\left( x \right)\text{d}x=3, \int\limits_{1}^{3}{f\left( x \right)\text{d}x=4}}$ thì $\int\limits_{2}^{3}{f\left( x \right)\text{d}x}$ bằng
A. 7.
B. 12.
C. 1.
D. $-1$.
A. 7.
B. 12.
C. 1.
D. $-1$.
Ta có $\int\limits_{2}^{3}{f\left( x \right)\text{d}x}=\int\limits_{2}^{1}{f\left( x \right)\text{d}x+\int\limits_{1}^{3}{f\left( x \right)\text{d}x=-3+4=1}}$.Đáp án C.