AB-A^2=B-I,
AB-B=A^2-I
(A-I)B=(A-I)(A+I)
B=A+I
=
2 1 5
0 4 -2
4 3 1
+
1 0 0
0 1 0
0 0 1
3 1 5
0 5 -2
4 3 2