Adjoint matrix (my function): ok with numbers but not symbolics

[salvomic]

hi,
in the code in this program the function adj(m) works well with numbers like

Code:

adj([1,2],[3,4])

but returns a "bad argument type" error with symbolic values like

Code:

adj([a,b],[c,d])

.
Why?

The need to have this function is because the new adjoint_matrix() in the CAS is, as it must be, more detailed, and it returns characteristic polynomial of A and the comatrix o A-xI, i.e.

Code:


adjoint_matrix([1,2],[4,3]);
[[1, -a-d, a*d-b*c], [ [[1],[0]], [[-d,b],[c,-a]] ] ]

that's correct, but isn't the simple desired form (only TRN(cofactors(mat)) ):

Code:

[[d, -b],[-c,a]]

Any help, please, using (or not) the new adjoint_matrix()?

Salvo