$\alpha (z)=-\overline{z}$
$\beta (z)=2-\overline{z}$
$\gamma (z)=\overline{z}$

${\displaystyle \begin{array}{ccc}\multicolumn{1}{c}{\gamma \beta \alpha (z)}& =& \gamma \beta (-\overline{z})\\ \multicolumn{1}{c}{}& =& \gamma (2-\overline{(-\overline{z})})\\ \multicolumn{1}{c}{}& =& \gamma (2+z)\\ \multicolumn{1}{c}{}& =& 2+\overline{z}\end{array}}$

Hence this combination of 3 reflections increases the x coordinates of each point in the shape by 2 units thus translating it 2 units forward while mapping each y coordinate to -y thus reflecting the shape in the real axis, so producing a glide reflection.