If write A^–1 in terms of A.

Given,

We know that A^-1 is given as: if |A| ≠ 0

|A| =

∴ A is invertible; now we can proceed to find the adj(A)

Adj(A) = transpose of co-factor matrix of A.

∴ Adj(A) =

We can observe by comparing A and adj(A) that:

Adj(A) = -A

∵ A^-1 =