博客中方程组和矩阵的 LaTeX 就会炸

$\begin{array}{cccc} 2 & 1 & -1 & 8\\ -3 & -1 & 2 & -11 \\ -2 & 1 & 2 & -3 \end{array}$

$\left\{ \begin{array}{} 2x + y - y=8 \\ \frac 1 2 y+ \frac1 2 z=1\\ -z = 1 \end{array} \right.$