Phép toán nào sau đây không thực hiện được:

\[\left( {\begin{array}{*{20}{c}}1&2\\5&0\end{array}\,\,\,\,\,\begin{array}{*{20}{c}}{ - 3}&6\\7&9\end{array}} \right) + \left( {\begin{array}{*{20}{c}}{ - 5}&1\\{ - 2}&8\end{array}\,\,\,\,\,\begin{array}{*{20}{c}}{ - 3}&0\\{ - 4}&2\end{array}} \right)\]

\[\left( {\begin{array}{*{20}{c}}1&{2\,\,\,\,\,5}\\3&{4\,\,\,\,\,\,7}\end{array}} \right) + \left( {\begin{array}{*{20}{c}}4&3\\2&9\end{array}} \right)\]

\[ - 3\left( {\begin{array}{*{20}{c}}1&2\\5&0\end{array}\,\,\,\,\,\begin{array}{*{20}{c}}{ - 3}&6\\7&9\end{array}} \right)\]

\[0\left( {\begin{array}{*{20}{c}}{ - 5}&1\\{ - 2}&8\end{array}\,\,\,\,\,\begin{array}{*{20}{c}}{ - 3}&0\\{ - 4}&2\end{array}} \right)\]