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If A is a square matrix such that A2 = I, then (A – I)3 + (A + I)3 – 7A is equal to : A. A B. I – A C. I + A D. 3A |
Answer» (A). A Expansion of the given expression, A3 – I3 + 3AI2 – 3A2I + A3 + I3 + 3AI2 + 3A2I – 7A 2A3 – 7A + 6AI2 2A2A – 7A + 6A 2AI – A {A2 = I} 2A – A A Option (A) is the answer. |
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