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If A=[1 3 2 1] , find the determinant of...

If `A=[1 3 2 1]` , find the determinant of the matrix `A^2-2Adot`

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`A^2=A.A=[[1,3],[2,1]][[1,3],[2,1]]`
`[[1+6,3+3],[2+2,6+1]]=[[7,6],[4,7]]`
`A^2-2A=[[7,6],[4,7]]-2[[1,3],[2,1]]`
`=[[7-2,6-6],[4-4,7-2]]`
`=[[5,0],[0,5]]`
`|A^2-2A|=[[5,0],[0,5]]`
`=25-0`
`=25`
...
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