Tính \(F\left( x \right) = \int {x{e^{\frac{x}{3}}}dx.} \) Chọn kết quả đúng
A.\(F\left( x \right) = 3\left( {x - 3} \right){e^{\frac{x}{3}}} + C\)
B.\(F\left( x \right) = \left( {x + 3} \right){e^{\frac{x}{3}}} + C\)
C.\(F\left( x \right) = \dfrac{{x - 3}}{3}{e^{\frac{x}{3}}} + C\)
D.\(F\left( x \right) = \dfrac{{x + 3}}{3}{e^{\frac{x}{3}}} + C\)