Square root algebra simplification

[Bingming]

HI, hopefully someone can help me. I have no idea how they got to the bottom simplification. I put in real numyers and it doesn't seem to make sense.

Thank you

 

[ksdhart2]

I've played with it some and I don't see the connection either. I suspect it's something to do with how these particular variables are defined. What's the context of this equation? What you've posted looks like one step of a multi-step process. What were the steps that immediately preceded it? What steps follow it?

 

[Bingming]

Thanks for replying. Hopefully you can make out these pictures! I think I must be missing something here. Can't work it out.