If 
and 
verify that (A + B) = (B + A).
A + B 
B + A 
= B + A
Therefore, A + B = B + A
This is true for any matrix
Conclusion: A + B = B + A
1
If and verify that (A + B) = (B + A).
A + B
B + A
= B + A
Therefore, A + B = B + A
This is true for any matrix
Conclusion: A + B = B + A