GATE 2011 CS (CS1) – Question 50
Find eigenvalues of $$\begin{pmatrix}1&2&3\\0&4&7\\0&0&3\end{pmatrix}.$$
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Correct answer: (A) 1,4,3
Explanation
For an upper-triangular matrix, det(λI−A) is the product of its diagonal factors, (λ−1)(λ−4)(λ−3). Therefore eigenvalues are diagonal entries 1,4,3, option A.