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If A=[1221]A = \begin{bmatrix}1 & 2\\2 & 1\end{bmatrix} and f(x)=x2−2x−3f(x) = x^2-2x-3, then f(A)f(A) is

Solution

✅ Correct Option: 2

A2=[5445]A^2=\begin{bmatrix}5&4\\4&5\end{bmatrix} and 2A=[2442]2A=\begin{bmatrix}2&4\\4&2\end{bmatrix}.

f(A)=A2−2A−3I=[5−2−34−4−04−4−05−2−3]=[0000]f(A)=A^2-2A-3I=\begin{bmatrix}5-2-3&4-4-0\\4-4-0&5-2-3\end{bmatrix}=\begin{bmatrix}0&0\\0&0\end{bmatrix}, the zero matrix.

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