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Câu hỏi: Cho $\int\limits_{1}^{2}{f\left( x \right)\text{d}x}=-3$ và $\int\limits_{2}^{3}{f\left( x \right)\text{d}x}=4$. Khi đó $\int\limits_{1}^{3}{f\left( x \right)\text{d}x}$ bằng
A. 12.
B. 7.
C. 1.
D. $-12$.
A. 12.
B. 7.
C. 1.
D. $-12$.
$\int\limits_{1}^{3}{f\left( x \right)\text{d}x}$ $=\int\limits_{1}^{2}{f\left( x \right)\text{d}x}+\int\limits_{2}^{3}{f\left( x \right)\text{d}x}$ $=-3+4$ $=1$.
Đáp án C.