Mathematics

Problem

G = \left\{ \begin{bmatrix} x & x \\ x & x \end{bmatrix} \right\}

x

is a non-zero real number is a group with respect to matrix multiplication. In this group, the inverse of

\begin{bmatrix} 1/3 & 1/3 \\ 1/3 & 1/3 \end{bmatrix}