2.Review of matrix operations
Addition and subtraction：Add or subtract the values of the corresponding row and column coordinates
Subtraction：Suppose that there are matrices X with dimensions n × m, and matrices Y with dimensions l × k, then
（1）Only when m = l is it feasible to multiply matrix X by matrix Y, and the resultant matrix XY exists；
（2）Only when k = n is it feasible to multiply matrix Y by matrix X, and the resultant matrix YX exists.
Formulas：
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Matrix transposition：Interchange of corresponding rows and columns.
