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-- Mathematics - Section B1
Matrices
If $A^3 =0$ such that $A^n≠ I$ for $1 ≤n≤4$, then $(I-A)^{-1}=?$
$A^4$
$A^3$
$I+A$
none of these
We have,
$A^4 (I-A) = A^4-A^5 = A^4-O = A^4 ≠I$
$A^3 (I-A) = A^3-A^4 ≠ I$
and, $(I + A) (I - A) = I-A^2 ≠ I$Hence, $(I-A)^{-1} ≠A^4, A^3, I+A$.