\( A=\left[\begin{array}{lll}2 & 1 & 1 \\ 1 & 2 & 1 \\ 1 & 1 & 2\end{array}\right] \)
Added by Abdulrehman B.
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det(A-λI) = \(\begin{vmatrix}2-λ & 1 & 1 \\ 1 & 2-λ & 1 \\ 1 & 1 & 2-λ\end{vmatrix}\) = (2-λ) \(\begin{vmatrix}2-λ & 1 \\ 1 & 2-λ\end{vmatrix}\) - \(\begin{vmatrix}1 & 1 \\ 1 & 2-λ\end{vmatrix}\) + \(\begin{vmatrix}1 & 2-λ \\ 1 & 1\end{vmatrix}\) = (2-λ) Show more…
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