Cho hàm số y=f(x) liên tục trên [a;b]

$A. \underset{a}{\overset{b}{\int }}f\left(x\right)dx+\underset{b}{\overset{a}{\int }}f\left(x\right)dx=0.$

$B. \underset{a}{\overset{b}{\int }}f\left(x\right)dx=\underset{b}{\overset{a}{\int }}\left|f\left(x\right)\right|dx.$

$C. \underset{a}{\overset{b}{\int }}f\left(x\right)dx=\underset{b}{\overset{a}{\int }}f\left(x\right)dx.$

$D. \underset{a}{\overset{b}{\int }}f\left(x\right)dx=\frac{1}{2}\underset{b}{\overset{a}{\int }}f\left(x\right)dx.$