AB = [1 2 ] [2 1 ] = [2+6 1+4] = [8 5]
[3 1 ] [3 2 ] [6+3 3+2] [9 5]
(AB)C = [8 5] [1 2 3] =[8+15 16+5 24+0]
[9 5] [3 1 0] [9+15 18+5 27+0]
= [23 21 24].
[24 23 27]. - I
BC = [2 1] [1 2 3] = [2+3 4+1 6+0]
[3 2] [3 1 0]. [3+6. 6+2. 9+0]
= [5. 5. 6]
[9. 8. 9]
A(BC) = [1 2]. [5. 5. 6] = [ 5+18 5+16 6+18]
[3 1]. [9. 8. 9] [15+9 15+8 18+9]
= [23. 21. 24]
[24. 23. 27]__II
From I and II (AB) C = A (BC)