octave:1> A = [1 2 3; 1 4 7; 3 -1 1]; B = [1 1 0; -1 1 1; 1 2 3]; C = [5 7 2; 3 3 0; 0 1 2];
octave:2> I = eye(3); M = [A I I; I B I; I I C];
octave:3> det(M)
ans = -1692.0
octave:4> det(A-I)*det(B-I)*det(C-I)*det(I+I/(A-I)+I/(B-I)+I/(C-I))
ans = -1692.0