The GATE Grind

GATE 2021 BM – Question 36

Engineering Mathematics · Linear Algebra · 2 marks · Multiple choice

A nonsingular 2×2 matrix A has trace 12 and determinant 32. Find the eigenvalues of A⁻¹.

  1. 0.6, 0.8
  2. 0.25, 0.125
  3. 6, 16
  4. 1/12, 1/32

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) 0.25, 0.125

Explanation

The characteristic equation is λ²−12λ+32=(λ−4)(λ−8)=0, so A has eigenvalues four and eight. Inverting a nonsingular matrix reciprocates its eigenvalues, giving one quarter and one eighth, or .25,.125. Thus B.

More Linear Algebra questions

All Linear Algebra questions →