(b) The relation between$\ \alpha\ and\ \beta\ $is
$\beta = \frac{\alpha}{1 - \alpha}$
Putting this value in the given equation, we have
$\frac{\beta - \alpha}{\alpha\beta} = \frac{\frac{\alpha}{1 - \alpha} - \alpha}{\alpha \bullet \frac{\alpha}{1 - \alpha}} = \frac{\alpha^{2}}{\alpha^{2}} = 1$