If \(A=\left[\begin{array}{ll}1 &2 \\ 2&1\end{array}\right]\) and \(f(x)=(I+x)(I-x)\) then \(f(A)\) is
Answer & explanation
Correct answer: option 1
$f(A)=(I-A)(I+A)$
$=\begin{bmatrix}0&-2\\-2&0\end{bmatrix}\begin{bmatrix}2&2\\2&2\end{bmatrix}$
\(=-4\left[\begin{array}{ll}1&1\\ 1&1 \end{array}\right]\)