Home > Matrix & Vector calculators > Inverse of matrix using Adjoint method example

1. Adjoint method example ( Enter your problem )
  1. Example `[[3,1,1],[-1,2,1],[1,1,1]]`
  2. Example `[[2,3,1],[0,5,6],[1,1,2]]`
  3. Example `[[2,3],[4,10]]`
  4. Example `[[5,1],[4,2]]`
Other related methods
  1. Adjoint method
  2. Gauss-Jordan Elimination method
  3. Cayley Hamilton method

2. Example `[[2,3,1],[0,5,6],[1,1,2]]`
(Next example)

1. Example `[[3,1,1],[-1,2,1],[1,1,1]]`





1. Find Inverse of matrix
`A=[[3,1,1],[-1,2,1],[1,1,1]]`


Solution:
`|A|` = 
 `3`  `1`  `1` 
 `-1`  `2`  `1` 
 `1`  `1`  `1` 


 =
 `3` × 
 `2`  `1` 
 `1`  `1` 
 `-1` × 
 `-1`  `1` 
 `1`  `1` 
 `+1` × 
 `-1`  `2` 
 `1`  `1` 


`=3 xx (2 × 1 - 1 × 1) -1 xx (-1 × 1 - 1 × 1) +1 xx (-1 × 1 - 2 × 1)`

`=3 xx (2 -1) -1 xx (-1 -1) +1 xx (-1 -2)`

`=3 xx (1) - -1 xx (-2) +1 xx (-3)`

`= 3 +2 -3`

`=2`


`Adj(A)` = 
Adj
`3``1``1`
`-1``2``1`
`1``1``1`


 = 
 + 
 `2`  `1` 
 `1`  `1` 
 - 
 `-1`  `1` 
 `1`  `1` 
 + 
 `-1`  `2` 
 `1`  `1` 
 - 
 `1`  `1` 
 `1`  `1` 
 + 
 `3`  `1` 
 `1`  `1` 
 - 
 `3`  `1` 
 `1`  `1` 
 + 
 `1`  `1` 
 `2`  `1` 
 - 
 `3`  `1` 
 `-1`  `1` 
 + 
 `3`  `1` 
 `-1`  `2` 
T


 = 
`+(2 × 1 - 1 × 1)``-(-1 × 1 - 1 × 1)``+(-1 × 1 - 2 × 1)`
`-(1 × 1 - 1 × 1)``+(3 × 1 - 1 × 1)``-(3 × 1 - 1 × 1)`
`+(1 × 1 - 1 × 2)``-(3 × 1 - 1 × (-1))``+(3 × 2 - 1 × (-1))`
T


 = 
`+(2 -1)``-(-1 -1)``+(-1 -2)`
`-(1 -1)``+(3 -1)``-(3 -1)`
`+(1 -2)``-(3 +1)``+(6 +1)`
T


 = 
`1``2``-3`
`0``2``-2`
`-1``-4``7`
T


 = 
`1``0``-1`
`2``2``-4`
`-3``-2``7`


`"Now, "A^(-1)=1/|A| × Adj(A)`

 = `1/(2)` ×
`1``0``-1`
`2``2``-4`
`-3``-2``7`


 = 
`1/2``0``-1/2`
`1``1``-2`
`-3/2``-1``7/2`



This material is intended as a summary. Use your textbook for detail explanation.
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2. Example `[[2,3,1],[0,5,6],[1,1,2]]`
(Next example)





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