det(A-1) = ?

A) I B) 1/detA

A-1 =(1/det(A)) .adj(A)

and we know that det(adj(A))=det(An-1 )where n is the order of the matrix

det(A-1) =det((1/det(A)).adj(A))

= (1/det(A))n x det(A)n-1

= 1/det(A)

= det(A) . An-1

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