3. Cayley Hamilton method example
( Enter your problem )
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- Example `[[3,1,1],[-1,2,1],[1,1,1]]`
- Example `[[2,3,1],[0,5,6],[1,1,2]]`
- Example `[[2,3],[4,10]]`
- Example `[[5,1],[4,2]]`
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Other related methods
- Adjoint method
- Gauss-Jordan Elimination method
- Cayley Hamilton method
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1. Example `[[3,1,1],[-1,2,1],[1,1,1]]`
1. Find Inverse of matrix using Cayley Hamilton method `A=[[3,1,1],[-1,2,1],[1,1,1]]`
Solution: To apply the Cayley-Hamilton theorem, we first determine the characteristic polynomial p(t) of the matrix A. `|A-tI|`
= | | `(3-t)` | `1` | `1` | | | `-1` | `(2-t)` | `1` | | | `1` | `1` | `(1-t)` | |
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`=(3-t)((2-t) × (1-t) - 1 × 1)-1((-1) × (1-t) - 1 × 1)+1((-1) × 1 - (2-t) × 1)`
`=(3-t)((2-3t+t^2)-1)-1((-1+t)-1)+1((-1)-(2-t))`
`=(3-t)(1-3t+t^2)-1(-2+t)+1(-3+t)`
`= (3-10t+6t^2-t^3)-(-2+t)+(-3+t)`
`=-t^3+6t^2-10t+2`
`p(t)=-t^3+6t^2-10t+2`
The Cayley-Hamilton theorem yields that `O = p(A)=-A^3+6A^2-10A+2I`
Rearranging terms, we have `:. 2I = A^3-6A^2+10A`
`:. 2I = A(A^2-6A+10I)`
`:. A^-1 = 1/2(A^2-6A+10I)`
Now, first we find `A^2-6A+10I`
`A^2` | = | `A×A` | = | | `3` | `1` | `1` | | | `-1` | `2` | `1` | | | `1` | `1` | `1` | |
| × | | `3` | `1` | `1` | | | `-1` | `2` | `1` | | | `1` | `1` | `1` | |
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= | | `3×3+1×-1+1×1` | `3×1+1×2+1×1` | `3×1+1×1+1×1` | | | `-1×3+2×-1+1×1` | `-1×1+2×2+1×1` | `-1×1+2×1+1×1` | | | `1×3+1×-1+1×1` | `1×1+1×2+1×1` | `1×1+1×1+1×1` | |
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= | | `9-1+1` | `3+2+1` | `3+1+1` | | | `-3-2+1` | `-1+4+1` | `-1+2+1` | | | `3-1+1` | `1+2+1` | `1+1+1` | |
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= | | `9` | `6` | `5` | | | `-4` | `4` | `2` | | | `3` | `4` | `3` | |
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`A^2` | = | | `3` | `1` | `1` | | | `-1` | `2` | `1` | | | `1` | `1` | `1` | |
| 2 |
| = | | `9` | `6` | `5` | | | `-4` | `4` | `2` | | | `3` | `4` | `3` | |
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`6 × A` | = | `6` | × | | `3` | `1` | `1` | | | `-1` | `2` | `1` | | | `1` | `1` | `1` | |
| = | | `18` | `6` | `6` | | | `-6` | `12` | `6` | | | `6` | `6` | `6` | |
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`A^2 - 6 × A` | = | | `9` | `6` | `5` | | | `-4` | `4` | `2` | | | `3` | `4` | `3` | |
| - | | `18` | `6` | `6` | | | `-6` | `12` | `6` | | | `6` | `6` | `6` | |
| = | | `9+18` | `6+6` | `5+6` | | | `-4-6` | `4+12` | `2+6` | | | `3+6` | `4+6` | `3+6` | |
| = | | `-9` | `0` | `-1` | | | `2` | `-8` | `-4` | | | `-3` | `-2` | `-3` | |
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`10 × I` | = | `10` | × | | `1` | `0` | `0` | | | `0` | `1` | `0` | | | `0` | `0` | `1` | |
| = | | `10` | `0` | `0` | | | `0` | `10` | `0` | | | `0` | `0` | `10` | |
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`A^2 - 6 × A + 10 × I` | = | | `-9` | `0` | `-1` | | | `2` | `-8` | `-4` | | | `-3` | `-2` | `-3` | |
| + | | `10` | `0` | `0` | | | `0` | `10` | `0` | | | `0` | `0` | `10` | |
| = | | `-9+10` | `0+0` | `-1+0` | | | `2+0` | `-8+10` | `-4+0` | | | `-3+0` | `-2+0` | `-3+10` | |
| = | | `1` | `0` | `-1` | | | `2` | `2` | `-4` | | | `-3` | `-2` | `7` | |
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Now, `A^-1 = 1/2(A^2-6A+10I)`
`:. A^-1 = ` | `1/(2)` | | `1` | `0` | `-1` | | | `2` | `2` | `-4` | | | `-3` | `-2` | `7` | |
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This material is intended as a summary. Use your textbook for detail explanation. Any bug, improvement, feedback then
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