inverse matrix: suppose a is an n-order square matrix on the number field. if there is another n-order matrix b on the same number field, such that: ab=ba=e. then we say that b is the inverse matrix of a, and a is called an invertible matrix. the necessary and sufficient condition for a to be an invertible matrix is ​​∣a∣≠0, that is, the invertible matrix is ​​a non-singular matrix. (when ∣a∣=0, a is called a singular matrix.

inverse matrix formula:

the calculation method is as follows: