Cho hàm số \(y=f(x)\) liên tục trên \(\left[ {a;b} \right]\) và thỏa mãn \(f\left( x \right) = f\left( {a + b - x} \right)\).

A. \(\int\limits_a^b {xf\left( x \right){\rm{d}}x}  =  - \frac{{a + b}}{2}\int\limits_a^b {f\left( x \right){\rm{d}}x} \)

B. \(\int\limits_a^b {xf\left( x \right){\rm{d}}x}  = \int\limits_a^b {f\left( x \right){\rm{d}}x} \)

C. \(\int\limits_a^b {xf\left( x \right){\rm{d}}x}  = \frac{{a + b}}{2}\int\limits_a^b {f\left( x \right){\rm{d}}x} \)

D. \(\int\limits_a^b {xf\left( x \right){\rm{d}}x}  = \left( {a + b} \right)\int\limits_a^b {f\left( x \right){\rm{d}}x} \)