Step-by-step explanation:
[tex]M=\left[\begin{array}{ccc}1&-1/f_2\\0&1\end{array}\right] \left[\begin{array}{ccc}1&0\\d&0\end{array}\right] \left[\begin{array}{ccc}1&-1/f_1\\0&1\end{array}\right]\\=\left[\begin{array}{ccc}1&-1/f_2\\0&1\end{array}\right]\left[\begin{array}{ccc}1&-1/f_1\\d&-d/f_1\end{array}\right]\\=\left[\begin{array}{ccc}1-d/f_2&-1/f_1+d/f_1f_2\\d&-d/f_1\end{array}\right]\\\\|M|=[-d/f_1+d^2/f_1f_2]-[-d/f_1+d^2/f_1f_2]=0\\\\-1/f=M_{12}=-1/f_1+d/f_1f_2\\1/f=M_{12}=+1/f_1-d/f_1f_2\\[/tex]
