Let $A=[a_{ij}]$ be $2 × 2 $ matrix, where $aij=\left\{\begin{matrix}1 & i≠j\\0 & i=j \end{matrix}\right.$, then
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $A^{22}-A^7+A=I$
$A=\begin{bmatrix}0&1\\1&0\end{bmatrix}$ [Given]
$⇒A^2=\begin{bmatrix}0&1\\1&0\end{bmatrix}\begin{bmatrix}0&1\\1&0\end{bmatrix}=\begin{bmatrix}1&0\\0&1\end{bmatrix}$
$⇒A^2=I$
$(A^2)^{11}=I^{11}$ $[I^n=I]$
$A^{22}=I$
Now,
$A^7=\begin{bmatrix}0&1\\1&0\end{bmatrix}$
$∴A^{22}-A^7=\begin{bmatrix}1&-1\\-1&1\end{bmatrix}$
$⇒A^{22}-A^7+A=\begin{bmatrix}1&-1\\-1&1\end{bmatrix}+\begin{bmatrix}0&1\\1&0\end{bmatrix}$
$=\begin{bmatrix}1&0\\0&1\end{bmatrix}=I$