A =

Cofactors of A are:

C₁₁ = – 3 C₂₁ = 6 C₃₁ = 6

C₁₂ = – 6 C₂₂ = 3 C₃₂ = – 6

C₁₃ = – 6 C₂₃ = – 6 C₃₃ = 3

adj A =

=

So, adj A =

Now, 3A^T = 3

Hence, adj A = 3.A^T