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I input my formula from Maxima and I need use
\pmatrix{1&-2&3\cr -1&1&-2\cr 2&-1&-1\cr }
I know to define matrix, should use
\left[ \begin{array}{ccc}
1 & -2 & 3 \\
-1 & 1 & -2 \\
2 & -1 & -1
\end{array} \right]
I have error: ! Package amsmath Error: Old form `\pmatrix' should be \begin{pmatrix ...