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Câu hỏi: Nếu $\int\limits_{0}^{7}{f\left( x \right)\text{d}x}=18$ và $\int\limits_{1}^{7}{f\left( x \right)\text{d}x}=9$ thì $\int\limits_{0}^{1}{f\left( x \right)\text{d}x}$ bằng
A. $9$.
B. $2$.
C. $27$.
D. $162$.
A. $9$.
B. $2$.
C. $27$.
D. $162$.
Ta có $\int\limits_{0}^{1}{f\left( x \right)\text{d}x}+\int\limits_{1}^{7}{f\left( x \right)\text{d}x}=\int\limits_{0}^{7}{f\left( x \right)\text{d}x}\Leftrightarrow \int\limits_{0}^{1}{f\left( x \right)\text{d}x}=\int\limits_{0}^{7}{f\left( x \right)\text{d}x}-\int\limits_{1}^{7}{f\left( x \right)\text{d}x}=18-9=9$.
Đáp án A.