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

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1.	If `A=[1 3 2 1]`, find the determinant of the matrix `A^2-2Adot`
Answer» `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` `\|A^2-2A\|=25`

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