8.
在\(\Delta ABC\)中,\(A={{60}^{\circ }},AB=3,AC=2.\)若\(\overrightarrow{BD}=2\overrightarrow{DC},\overrightarrow{AE}=\lambda \overrightarrow{AC}-\overrightarrow{AB}(\lambda \in R),\)且\(\overrightarrow{AD}\bullet \overrightarrow{AE}=6\),则\(\lambda \)值为( )