Q. 154.3( 25 Votes )

If A is square ma A. A

B. I – A

C. I

D. 3A

Answer :

Given that A2 = A

Calculating value of (I + A)3  – 7 A:


⇒ I3 + A3 + 3I2A + 3IA2 – 7A


⇒ I + A2.A + 3A + 3A2 – 7A (In = I and I.A = A)


⇒ I + A.A + 3A + 3A – 7A (A2 = A)


⇒ I + A2 + 3A + 3A – 7A


⇒ I + A - A


⇒ I


Hence (I + A)3 – 7 A = I.

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