Bessel's Equality and Inequality

[MathBoi]

Hi I'm in the process of trying to understand the proof to bessel's equality and inequality and I am stuck, I have got to the line
[URL=http://img141.imageshack.us/i/besselsequality.jpg/][PLAIN]http://img141.imageshack.us/img141/396/besselsequality.jpg[/URL] Uploaded with ImageShack.us[/PLAIN]
and I'm not entirely sure how it equates to the next line but according to some of the books I have been reading it does for some reason

If anyone could explain how it would be awesome!
Thanks Very much :)

 

[dextercioby]

Who's \alpha ? Wiki's article is pretty clear http://en.wikipedia.org/wiki/Bessel's_inequality