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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: O...