"In the complete factorization of $y^2 - 4 - x^2 + 4x$, one of it's factors is"
A) $x - 4$
B) $y + 2$
C) $y - x - 2$
D) $y - x + 2$
I did a little calculator trick I always use. I got it wrong. I've decided to study more deeply the steps required to properly answer this manually.
However, unfortunately I couldn't understand what someone explained to me a while back. Can someone enlighten me here? I find it puzzling how to get the complete factorization of such thing.
Btw, I chose D. Got it wrong. I believe it was C after some extra calculation, but I am not sure anymore...