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CUET · MATHS · PYQ PAPER 2023

If A is a square matrix of order \(3 \times 3\) such that \(A^2 = A\) and I is the unit matrix of order \(3 \times 3\), then the value of \((I - A)^3 + A^2 + I\) is:

  1. A \(0\)
  2. B \(I\)
  3. C \(2I\)
  4. D \(4I\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(2I\)

Step-by-step Solution

Detailed explanation

\((I - A)^3 = I^3 - 3I^2A + 3IA^2 - A^3 = I - 3A + 3A^2 - A^3\) \(A^2 = A \implies A^3 = A^2 \cdot A = A \cdot A = A^2 = A\) \((I - A)^3 = I - 3A + 3A - A = I - A\) \((I - A)^3 + A^2 + I = (I - A) + A + I\) \(= I - A + A + I = 2I\)