So I've been out of the loop of math for some 4 years, and now I'm back in college doing math. Everyone loves math!

So lets discuss something I'm wondering about.

y(2)-y(1)

________

x(2)-x(1)

Can this equation be reversed ?

Can we do

y(1)-y(2)

________

x(1)-x(2)

I'm under the assumption that you can, based only on the fact that in the previous week or two I swear I read something that told me you could, SO LONG as you remained uniform (ie didn't do y(2)-y(1) over x(1)-x(2)

But my buddy thinks you can't swap it.

Can I get some clarification?

(Yes I am aware that y=mx+b is the actual slope intercept form, but I'm discussing how to get it into that form)