If A is a square matrix such that A2 = A, then (I + A)3 – 7A is equal to

(I + A)3 = I3 + A3 + 3A2I + 3AI2 (Using the identity of (a + b)3 = a3 + b3 + 3ab (a + b))


(I + A)3 = I + A2(A) + 3AI + 3A [I stands for Identity Matrix]


(I + A)3 = I + A2 + 3A + 3A


(I + A)3 = 7A + I


(I + A)3 – 7A


7A + I – 7A


= I


Option (C) is the answer.

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