the last one isnt true.

Since a+a=a+b, a must = b

so 2(a-b) would be 2(0) while a-b would also be 0, so:

2(a-b)=a-b

2(0)=0

0=0

you can't divide by 0...-2b didn't go anywhere....b-2b=-b

don't question my God question your math skills.

or lack thereof.

explain to me where -2b went and i'll explain to you where God is

what happened to -2b?

-2b just can't disappear.

fail... a-b = 0 as stated by the first equation...