Exercise Show that if a squarematrix A has an inverse, it must be unique.

The unique inverse of square matrix A, denotedby A-1, is given by               

Note carefully the order of the indices in adj(A), the adjoint matrix of A, with the column number preceding the row number. Thematrix (Aij)n×n iscalled the cofactor matrix, whose transpose is the adjoint matrix.

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