If \(A=\left[\begin{array}{ll}1 &2 \\ 2&1\end{array}\right]\) and \(f(x)=(I+x)(I-x)\) then \(f(A)\) is

\(-4\left[\begin{array}{ll}1&1\\ 1&1 \end{array}\right]\) \(-8\left[\begin{array}{ll}1&1\\ 1&1 \end{array}\right]\) \(4\left[\begin{array}{ll}1&1\\ 1&1 \end{array}\right]\) None

\(-4\left[\begin{array}{ll}1&1\\ 1&1 \end{array}\right]\)

$f(A)=(I-A)(I+A)$ $=\begin{bmatrix}0&-2\\-2&0\end{bmatrix}\begin{bmatrix}2&2\\2&2\end{bmatrix}$ \(=-4\left[\begin{array}{ll}1&1\\ 1&1 \end{array}\right]\)