A + B = (        )
 2  1  4
-1  6  5

-1  3  3 ,   1
2A + 1
3B = 1
6(             )
     5   1  9
   - 5  14  9

   - 4   7  6 , °AB = (          )
   0  0  0
   0  0  0

   0  0  0 ,   BA = (         )
-11  6  - 1
-22 12  - 2
-11  6  - 1 .