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GATE 2025 MA – Question 16

Ordinary Differential Equations · Stability and Eigenvalue Problems · 1 mark · Multiple choice

For X′=MX with M any real skew-symmetric 6×6 matrix, when is the origin stable?

  1. For every such M
  2. Only rank 2
  3. Only rank 4
  4. Only rank 6

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Correct answer: (A) For every such M

Explanation

Along a solution, $d\|X\|_2^2/dt=X^T(M+M^T)X=0$. Distance from the origin stays constant, so any sufficiently small initial condition remains small. Lyapunov stability holds for every rank, though asymptotic stability generally does not. **A**.

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