irishda said:
Actually multiply 9 by .999r though and see what you come up with.
That's just a red herring, as I said before, you just grasping at statements made in the proof, rather than at the reasoning between those statements.
Yes, the proof
says that 9x = 9 where x = 0.999..., but that claim is
not just pulled out the air, it is
deduced from the previous statements. You can't just attack the statement while ignoring the reasoning the produced it.
Anyway, here's a subtly different way of arriving and the same claim:
0.999... * 10 - 0.999... = 0.999... * 9
Agreed? I mean, that's pretty basic, if you take a number and multiply by 10, then take one lot of that number away, you've got the number multiplied by 9 instead.
0.999... * 10 - 0.999... = 9.999... - 0.999... = 9
0.999... * 9 = 8.999...
I should hope these are both clearly true too.
So, one side of the original equation equals 9, and the other equals 8.999..., also, we know from the first part that the two sides are also equal to each other.
Therefore 9 and 8.999... must also be equal.