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GATE 2026 ES – Question 37

Mathematics Foundation · Linear Algebra · 2 marks · Multiple choice

Find the eigenvalues of $A=\begin{pmatrix}2&2&3\\2&5&6\\3&4&10\end{pmatrix}$.

  1. $1,8-\sqrt{37},-8+\sqrt{37}$
  2. $2,8-\sqrt{37},-8+\sqrt{37}$
  3. $1,8+\sqrt{37},8-\sqrt{37}$
  4. $2,8+\sqrt{37},8+\sqrt{37}$

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Correct answer: (C) $1,8+\sqrt{37},8-\sqrt{37}$

Explanation

Expanding $\det(\lambda I-A)$ gives $\lambda^3-17\lambda^2+43\lambda-27=(\lambda-1)(\lambda^2-16\lambda+27)$. The quadratic roots are $(16\pm\sqrt{256-108})/2=8\pm\sqrt{37}$. Thus **C**. Their sum is 17,the trace, and their product is 27,the determinant.

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