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Câu hỏi: Nếu $\int_{2}^{5}{f\left( x \right)}\text{d}x=3$ và $\int_{2}^{5}{g\left( x \right)}\text{d}x=5$ thì $\int_{2}^{5}{\left[ f\left( x \right)+g\left( x \right) \right]}\text{d}x$ bằng
A. $15.$
B. $8.$
C. $3.$
D. $5.$
A. $15.$
B. $8.$
C. $3.$
D. $5.$
Ta có: $\int_{2}^{5}{\left[ f\left( x \right)+g\left( x \right) \right]}\text{d}x=\int_{2}^{5}{f\left( x \right)}\text{d}x+\int_{2}^{5}{g\left( x \right)}\text{d}x=3+5=8.$
Đáp án B.