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GATE 2024 BM – Question 36

Engineering Mathematics · Linear Algebra · 2 marks · Multiple choice

Find the eigenvalues of $A=\begin{pmatrix}1&-1\\2&-2\end{pmatrix}$.

  1. −1 and 0
  2. −1 and +1
  3. −1 and −1
  4. +1 and 0

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Correct answer: (A) −1 and 0

Explanation

The rows are proportional, so determinant is zero and one eigenvalue is zero. The trace is −1, equal to the eigenvalue sum, giving the other eigenvalue −1. Equivalently the characteristic polynomial is λ(λ+1). Thus A.

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