|A| =

= 2(4 – 1) + 1( – 2 + 1) + 1(1 – 2)

= 6 – 2

= – 4

Hence, A ^{– 1} exists

Cofactors of A are:

C₁₁ = 3 C₂₁ = 1 C₃₁ = – 1

C₁₂ = + 1 C₂₂ = 3 C₃₂ = 1

C₁₃ = – 1 C₂₃ = 1 C₃₃ = 3

adj A =

=

So, adj A =

Now, A ^{– 1} = .adj A

So, A ^{– 1} = .

Hence, A ^{– 1} =