\(14.\)已知\( \overrightarrow{a}=(1,2,-2)\)，\( \overrightarrow{b}=(1,0,-1)\)，求\(( \overrightarrow{a}-2 \overrightarrow{b})\cdot (2 \overrightarrow{a}+ \overrightarrow{b})=\) ______ ．