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GATE 2023 ES – Question 12

Mathematics Foundation · Linear Algebra · 1 mark · Multiple choice

For square matrices P, Q, consider X:$(P^{-1})^{-1}=P$ and Y:Q is symmetric if $Q=-Q^T$. Choose the truth values.

  1. X true;Y false
  2. X false;Y true
  3. Both true
  4. Both false

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Show answer and explanation

Correct answer: (A) X true;Y false

Explanation

For invertible P, inverting its inverse returns P, so X is true under the implicit invertibility condition. The relation $Q=-Q^T$ defines skew-symmetry, whereas symmetry requires $Q=Q^T$. Therefore Y is false in general. Select **A**.

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