Since completing the square has a lot of steps and it’s easy to forget some of them after a while, I went back and made a video for this topic.
See http://blip.tv/file/4866146 (5 minutes and 7 seconds)
It shows how you go from a standard quadratic function equation into the vertex form, assuming that you are familiar with the expansion “shortcut” that (x + a)2 = x2 + 2ax + a2.
By the way, are you having trouble streaming the videos? If so, try pausing it as soon as it starts to auto-play, and waiting a few minutes before you return to the computer to view it. Generally, video files that stream over the internet are already in formats that allow you to load them quickly, so it shouldn’t take more than a few minutes to load each video.