Google
Câu hỏi: Cho $\int\limits_{a}^{c}{f\left( x \right)\text{d}x=50}$, $\int\limits_{b}^{c}{f\left( x \right)\text{d}x=20}$. Tính $\int\limits_{b}^{a}{f\left( x \right)\text{d}x}$.
A. $-30$.
B. $0$.
C. $70$.
D. $30$.
A. $-30$.
B. $0$.
C. $70$.
D. $30$.
Ta có $\int\limits_{b}^{a}{f\left( x \right)\text{d}x}$ $=\int\limits_{b}^{c}{f\left( x \right)\text{d}x}+\int\limits_{c}^{a}{f\left( x \right)\text{d}x}=\int\limits_{b}^{c}{f\left( x \right)\text{d}x}-\int\limits_{a}^{c}{f\left( x \right)\text{d}x}$ $=20-50=-30$.
Đáp án A.