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CUET · MATHS · PYQ PAPER 2025

If A is a square matrix and I is the identity matrix of same order such that \(A^2=I\), then \((A-I)^3+(A+I)^3-3 A\) is equal to:

  1. A \(A\)
  2. B \(2A\)
  3. C \(3A\)
  4. D \(5A\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(5A\)

Step-by-step Solution

Detailed explanation

\( (A-I)^3+(A+I)^3 = 2A^3 + 6AI^2 \) \( = 2(A^2 A) + 6A(I) \) \( = 2(IA) + 6A \) \( = 2A + 6A = 8A \) \( (A-I)^3+(A+I)^3-3 A = 8A - 3A = 5A \)
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