JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Matrices

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Let and . If denotes the sum of all diagonal elements of the matrix , then has value equal to:
  1. (A)1
  2. (B)2✓ Correct
  3. (C)3
  4. (D)0

Answer: (B)

Solution

The trace is linear, so taking traces of both given equations turns them into two scalar equations:

Solving the pair gives and , so

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Single correct option

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