If A=(1236)A = \begin{pmatrix} 1 & 2 \\ 3 & 6 \end{pmatrix}A=(1326), what is the result of R2←R2−3R1R_2 \leftarrow R_2 - 3R_1R2←R2−3R1?
(1200)\begin{pmatrix} 1 & 2 \\ 0 & 0 \end{pmatrix}(1020)
(1203)\begin{pmatrix} 1 & 2 \\ 0 & 3 \end{pmatrix}(1023)
(120−6)\begin{pmatrix} 1 & 2 \\ 0 & -6 \end{pmatrix}(102−6)
(0036)\begin{pmatrix} 0 & 0 \\ 3 & 6 \end{pmatrix}(0306)