Hence
I don't see how.
You can derive it from the last statement
(E-Q_{n+1})-(E-Q_n) = Q_n - Q_{n+1}
Hence, if
(1 - \frac{E-Q_n}{E}) = (\frac{Q_n}{E})
the conclusion is correct. If you split the first part in
(1- \frac{E}{E} + \frac{Q_n}{E})
you'll see this is the case.
Something seems wrong with either my latex or the forums compiler, so i'll leave it this way.
Hope this helps.