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Câu hỏi: Nếu $\int\limits_{-1}^{0}{f\left( x \right)\text{d}x=1, }\int\limits_{0}^{1}{f\left( x \right)\text{d}x=2 }$ thì $\int\limits_{-1}^{1}{2f\left( x \right)\text{d}x }$ bằng
A. $6$.
B. $4$.
C. $0$.
D. $3$.
A. $6$.
B. $4$.
C. $0$.
D. $3$.
Ta có $\int\limits_{-1}^{1}{2f\left( x \right)\text{d}x }=2\int\limits_{-1}^{1}{f\left( x \right)\text{d}x=2\left( \int\limits_{-1}^{0}{f\left( x \right)\text{d}x+}\int\limits_{0}^{1}{f\left( x \right)\text{d}x } \right) =2\cdot 3=6}$.
Đáp án A.