Cho \(\int\limits_{ - 1}^2 {f\left( x \right)dx} = 3\)và \(\int\limits_2^{ - 1} {g\left( x \right)dx} = 1\). Tính \(I = \int\limits_{ - 1}^2 {\left[ {x + 2f\left( x \right) - 3g\left( x \right)} \right]dx} \)
A.\(\dfrac{5}{2}\)
B.\(\dfrac{{21}}{2}\)
C.\(\dfrac{{26}}{2}\)
D.\(\dfrac{7}{2}\)