设向量组: $\alpha_1=\left[\begin{array}{c}-9 \\ 1 \\ 1 \\ 1\end{array}\right], \alpha_2=\left[\begin{array}{c}2 \\ -8 \\ 2 \\ 2\end{array}\right], \alpha_3=\left[\begin{array}{c}3 \\ 3 \\ -7 \\ 3\end{array}\right], \alpha_4=\left[\begin{array}{c}4 \\ 4 \\ 4 \\ -6\end{array}\right]$, 求此向量组的秩和一个极大线性无关组, 并将其余的向量用该 极大线性无关组表示.