Cho 3 vecto \(\overrightarrow{a},\overrightarrow{b},\overrightarrow{c}\) thỏa mãn \(\overrightarrow{\left|a\right|}=1,\left|\overrightarrow{b}\right|=2,\left|\overrightarrow{a-b}\right|=3\) . Tính \(\left(\overrightarrow{a}-2\overrightarrow{b}\right)\left(2\overrightarrow{a}+\overrightarrow{b}\right)\)