irishda said:
Except they're proofs with logical fallacies, like saying "All cats are red. I have a cat. Therefore I have a red cat." I've already refuted the algebraic proof, and, while I don't have the necessary knowledge to refute the fraction, I did explain it to someone else who was knowledgeable enough to be able to laugh at it.
Actually, if you make the assumption all cats are red, there's no logical problems with that argument. Now, if you'd said something like "All cats are red. I have a red pet. Therefore I have a cat," then yes, there is a logical fallacy there. But this is just me being pedantic and has no bearing on the topic really.
I'm not trying to be rude but you have refuted nothing, because you made errors in your attempt at a disproof (as you must have, because this is a fact. I cannot stress this enough, this is a
widely accepted mathematical fact. I study maths, this is what I do).
If we define x = 0.999... (which we can do, because we are awesome and have the power to set the value of variables, we are not in this instance presupposing 0.999... = 1, it simply falls out of the maths), then the following process makes complete sense.
x = 0.999...
10*x = 10 * 0.999...
10x = 9.999... (if you disagree with this step, one of us is doing algebra very, very wrong)
10x - x = 9.999... - x (at this stage, remember that we DEFINED x = 0.999...)
9x = 9 (this seems to be what you're disagreeing with, but it seems elementary to me that 9.999... - 0.999... = 9. If you'd like, you can look at it a different way; (9 + 0.9 + 0.09 + 0.009 + ...) - (0.9 + 0.09 + 0.009 + ...) = 9. You can see clearly that 0.9 subtracts from 0.9 to leave 0, and 0.09 subtracts from 0.09 to leave 0 and so on, until all we are left with is 9).
And obviously from here,
x = 1, meaning 0.999... = 1.