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Câu hỏi: Nếu ${\int\limits_{1}^{5}{f\left( x \right) }\text{d}x=-2}$ và ${\int\limits_{5}^{7}{f\left( x \right) }\text{d}x=6}$ thì ${\int\limits_{1}^{7}{f\left( x \right) }\text{d}x}$ bằng
A. $-12.$
B. $-8.$
C. $4.$
D. $8.$
A. $-12.$
B. $-8.$
C. $4.$
D. $8.$
$\int\limits_{1}^{7}{f\left( x \right) }\text{d}x=\int\limits_{1}^{5}{f\left( x \right) }\text{d}x+\int\limits_{5}^{7}{f\left( x \right) }\text{d}x=-2+6=4.$
Đáp án C.