Now, this is a total contradiction. Even if (c+r) is INFINITELY BIG, 0*(c+r) will NEVER equal 5. You can't add 0 to itself infinite times. However 0.000000000(lots of zeroes)000001*(something else) will eventually become 5 if (something else) is big enough.
What about -5/0?
Now, -5/0 = 5/-0 = 5/0.
5 = 0*(c+r). c+r is approaching NEGATIVE infinity as b is approaching zero. (think y=5/x). 0 * negative large number = 5 ? Even more ridiculous.
Hope this sheds some light. Just think about it algebraically and it all makes sense (or in this case... very clearly doesn't make sense, which is what I wanted). Proof by contradiction - we started out assuming (c+r) was an integer, but no such integer solves 5 = 0*(c+r), therefore assumption is false, which is what we were trying to prove.