Given matrix is \[\begin{bmatrix}6&0&0&0\\9&-8&0&0\\0&1&2&0\\6&8&-6&2\end{bmatrix}\]

which is triangular matrix:

The principd diagonal elements are eigen values

\(\displaystyle\Rightarrow{6},-{8},{2},{2}\) are eigen values

with 2 is multiply 2 elements

which is triangular matrix:

The principd diagonal elements are eigen values

\(\displaystyle\Rightarrow{6},-{8},{2},{2}\) are eigen values

with 2 is multiply 2 elements