If $A^2-A+I=0$, then the inverse of $A$ is

If $A^2-A+I=0$, then the inverse of $A$ is
  1. $A+I$
  2. $A$
  3. $A-I$
  4. $I-A$

Solution

Given $A^2-A+I=0$ $A^{-1} A^2-A^{-1} A+A^{-1}-I=A^{-1} \cdot 0$ (Multiplying $A^{-1}$ on both sides) $\Rightarrow A-I+A^{-1}=0$ or $A^{-1}=I-A$

Asked in: JEE Main 2005

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