Given A=(1326)A = \begin{pmatrix} 1 & 3 \\ 2 & 6 \end{pmatrix}A=(1236), which vector x=(x1x2)x = \begin{pmatrix} x_1 \\ x_2 \end{pmatrix}x=(x1x2) lies in the null space of AAA?
(3−1)\begin{pmatrix} 3 \\ -1 \end{pmatrix}(3−1)
(11)\begin{pmatrix} 1 \\ 1 \end{pmatrix}(11)
(13)\begin{pmatrix} 1 \\ 3 \end{pmatrix}(13)
(62)\begin{pmatrix} 6 \\ 2 \end{pmatrix}(62)