Google
Câu hỏi: Nếu $\int\limits_{1}^{2}{f\left( x \right)\text{d}x}=-1$ và $\int\limits_{2}^{5}{f\left( x \right)\text{d}x}=3$ thì $\int\limits_{1}^{5}{-2f\left( x \right)\text{d}x}$ bằng
A. $-2$.
B. $-4$.
C. $4$.
D. $2$.
A. $-2$.
B. $-4$.
C. $4$.
D. $2$.
Ta có: $\int\limits_{1}^{5}{-2f\left( x \right)\text{d}x}=-2\int\limits_{1}^{5}{f\left( x \right)\text{d}x}=-2\left( \int\limits_{1}^{2}{f\left( x \right)\text{d}x}+\int\limits_{2}^{5}{f\left( x \right)\text{d}x} \right)=-2\left( -1+3 \right)=-4$.
Đáp án B.