1. Division of matrix
1.
AB=A⋅B-1
2.
BA=B⋅A-1
Examples
1. Find BA ...
A=[231056112],B=[21-110-1112]Solution:=2×(5×2-6×1)-3×(0×2-6×1)+1×(0×1-5×1)=2×(10-6)-3×(0-6)+1×(0-5)=2×(4)-3×(-6)+1×(-5)=8+18-5=21 = | | +(5×2-6×1) | -(0×2-6×1) | +(0×1-5×1) | | | -(3×2-1×1) | +(2×2-1×1) | -(2×1-3×1) | | | +(3×6-1×5) | -(2×6-1×0) | +(2×5-3×0) | |
| T |
|
= | | +(10-6) | -(0-6) | +(0-5) | | | -(6-1) | +(4-1) | -(2-3) | | | +(18-5) | -(12+0) | +(10+0) | |
| T |
|
Now, A-1=1|A|×Adj(A) = | | 0.1905 | -0.2381 | 0.619 | | | 0.2857 | 0.1429 | -0.5714 | | | -0.2381 | 0.0476 | 0.4762 | |
|
B×(A-1) | = | | × | | 0.1905 | -0.2381 | 0.619 | | | 0.2857 | 0.1429 | -0.5714 | | | -0.2381 | 0.0476 | 0.4762 | |
|
= | | 2×0.1905+1×0.2857-1×-0.2381 | 2×-0.2381+1×0.1429-1×0.0476 | 2×0.619+1×-0.5714-1×0.4762 | | | 1×0.1905+0×0.2857-1×-0.2381 | 1×-0.2381+0×0.1429-1×0.0476 | 1×0.619+0×-0.5714-1×0.4762 | | | 1×0.1905+1×0.2857+2×-0.2381 | 1×-0.2381+1×0.1429+2×0.0476 | 1×0.619+1×-0.5714+2×0.4762 | |
|
= | | 0.381+0.2857+0.2381 | -0.4762+0.1429-0.0476 | 1.2381-0.5714-0.4762 | | | 0.1905+0+0.2381 | -0.2381+0-0.0476 | 0.619+0-0.4762 | | | 0.1905+0.2857-0.4762 | -0.2381+0.1429+0.0952 | 0.619-0.5714+0.9524 | |
|
= | | 0.9048 | -0.381 | 0.1905 | | | 0.4286 | -0.2857 | 0.1429 | | | 0 | 0 | 1 | |
|
This material is intended as a summary. Use your textbook for detail explanation.
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