设 $\alpha_1=\left(\begin{array}{l}a \\ 1 \\ 1\end{array}\right), \alpha_2=\left(\begin{array}{l}1 \\ a \\ 1\end{array}\right), \alpha_3=\left(\begin{array}{l}1 \\ 1 \\ a\end{array}\right), \alpha_4=\left(\begin{array}{c}1 \\ 1 \\ -2\end{array}\right)$ 且 $\alpha_1, \alpha_2, \alpha_3$与 $\alpha_2, \alpha_3, \alpha_4$ 等价，则 $a$ 满足