For which value of $ x $, the matrix $ A $ has no inverse where $$ A = \begin{pmatrix} 8 & x & 0 \\4 & 0 & 2 \\12 & 6 & 0 \end{pmatrix} $$
If $$ A = \begin{pmatrix} -5 & -8 & 0 \\3 & 5 & 0 \\1 & 2 & -1 \end{pmatrix} $$ then $ A^2 $ is: