Find eigenvalues of matrix:
$$ A = \left[ \begin{matrix}3&0&1\\9&-1&2\\-9&4&-1\end{matrix} \right] $$The eigenvalues of matrix A are:
$$ \lambda_1 = 3 ~ \text{ , } ~ \lambda_2 = -1+i ~ \text{ and } ~ \lambda_3 = -1-i $$Step 1 : The characteristic polynomial for matrix A is:
$$ p(\lambda) = -\lambda^3+\lambda^2+4\lambda+6 $$
Step 2 : Eigenvalues are roots of the characteristic polynomial, so the equation
$$ -\lambda^3+\lambda^2+4\lambda+6 = 0 $$yields the above eigenvalues.
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