A=
0 B
C 0
A^-1 =
0 C^-1
B^-1 0
=
0 0 -1/3 1
0 0 2/3 -1
1 -2 0 0
0 1 0 0
|A| = (-1)^(2*2) |B||C| = -3
(A*)^-1 = (1/|A|) A = -1/3 A
A=
0 B
C 0
A^-1 =
0 C^-1
B^-1 0
=
0 0 -1/3 1
0 0 2/3 -1
1 -2 0 0
0 1 0 0
|A| = (-1)^(2*2) |B||C| = -3
(A*)^-1 = (1/|A|) A = -1/3 A