Which of the following is an eigenvector for A=(1221)A = \begin{pmatrix} 1 & 2 \\ 2 & 1 \end{pmatrix}A=(1221)?
(11)\begin{pmatrix} 1 \\ 1 \end{pmatrix}(11)
(1−1)\begin{pmatrix} 1 \\ -1 \end{pmatrix}(1−1)
(12)\begin{pmatrix} 1 \\ 2 \end{pmatrix}(12)
(00)\begin{pmatrix} 0 \\ 0 \end{pmatrix}(00)