CUET · MATHS · PYQ PAPER 2025
If A is a square matrix such that \(A^2=A\) and I is the identity matrix of same order as A, then the value of
\((A-2 I)^2-(2 A+I)^2+11 A\) is :
- A \(I\)
- B \(2I\)
- C \(3I\)
- D \(-I\)
Answer & Solution
Correct Answer
(C) \(3I\)
Step-by-step Solution
Detailed explanation
\((A-2 I)^2 = A^2 - 4AI + 4I^2 = A - 4A + 4I = -3A + 4I\) \((2 A+I)^2 = 4A^2 + 4AI + I^2 = 4A + 4A + I = 8A + I\) \((A-2 I)^2-(2 A+I)^2+11 A = (-3A + 4I) - (8A + I) + 11A\) \(= -3A + 4I - 8A - I + 11A\) \(= (-3 - 8 + 11)A + (4 - 1)I\) \(= 0A + 3I = 3I\)
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