# Basic Maths Grand Test- Q6

If $A$ is a square matrix such that $A^2 = A$ , then $(I+A)^3 - 7A equals$

A. $I-A$

B. $I$

C. $A$

D. $3A$

reshown Nov 20

ANS should be B.

(I+A) ^3= I^3 + A^3 + 3I^2A + 3IA^2 = I + A + 3A + 3A = I+ 7A     [ A^2= A, A^3= A^2 *A= A^2= A]

Therefore=  I +7A - 7A=  I

answered Nov 20 by (13,760 points)