(2) Orthogonally diagonalize the following matrix by finding the diagonal matrix D and orthogonal matrix P such that $A = PDP^T$. $$A = \begin{bmatrix} 2 & 2 & 1 \\ 2 & -1 & -2 \\ 1 & -2 & 2 \end{bmatrix}$$ (Hint: The eigenvalues are $\lambda = 3, 3, -3$.)
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For $\lambda = 3$, we solve $(A - 3I)v = 0$: $$A - 3I = \begin{bmatrix} 2-3 & 2 & 1 \\ 2 & -1-3 & -2 \\ 1 & -2 & 2-3 \end{bmatrix} = \begin{bmatrix} -1 & 2 & 1 \\ 2 & -4 & -2 \\ 1 & -2 & -1 \end{bmatrix}$$ The rows are linearly dependent, so we have $-x + 2y + z Show more…
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