Hello,

I am studying to take a math placement exam in two days. There's this one geometry problem that I cannot figure out how to solve. I watched a video of someone solving it but I don't understand what they're doing after a certain point. Here's the problem:

I don't know if it's just me but I think his approach to solve it is way too complicated. Does anybody know another way to solve this problem other than what he's doing? I know how to factor well but even with that what he's doing is still confusing me. I'll leave screenshots of what the guy in the video did but I am drawing a blank in this one.

(I understand what he did up to this picture, after that I don't really know why he's doing all that)

Here's the rest of his work: