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GATE 2023 MA – Question 22

Linear Algebra · Eigenvalues and Canonical Forms · 1 mark · Multiple choice

T:ℝ⁴→ℝ⁴ has kernel {4x₁+3x₂+2x₃+x₄=0} and rank(T−3I)=3. Find its minimal polynomial.

  1. x(x−3)
  2. x(x−3)³
  3. x³(x−3)
  4. x²(x−3)²

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Correct answer: (A) x(x−3)

Explanation

The zero eigenspace has dimension 3 and the eigenvalue-3 eigenspace has dimension 1. Their intersection is zero, so their direct sum has dimension 4. T is diagonalizable with both eigenvalues present, giving **x(x−3), A**.

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