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Câu hỏi: Nếu $\int\limits_{1}^{2}{f\left( x \right) \text{d}x}=5,\int\limits_{3}^{5}{f\left( x \right) \text{d}x}=-2$ thì $\int\limits_{1}^{5}{f\left( x \right) \text{d}x}$ bằng
A. $-7.$
B. $-2.$
C. $7.$
D. $3.$
A. $-7.$
B. $-2.$
C. $7.$
D. $3.$
Ta có $\int\limits_{1}^{5}{f\left( x \right) \text{d}x}=\int\limits_{1}^{3}{f\left( x \right) \text{d}x}+\int\limits_{3}^{5}{f\left( x \right) \text{d}x}=5+\left( -2 \right)=3.$
Đáp án D.