[31−1−7]\left[\begin{array}{rr}3 & 1 \\-1 & -7\end{array}\right][3−11−7]
[−31−1−7]\left[\begin{array}{cc}-3 & 1 \\-1 & -7\end{array}\right][−3−11−7]
[3−1−1−7]\left[\begin{array}{rr}3 & -1 \\-1 & -7\end{array}\right][3−1−1−7]
[311−7]\left[\begin{array}{rr}3 & 1 \\1 & -7\end{array}\right][311−7]