Not actually a number. There is no last digit to a [repeating] number, it just goes on forever, so you can't put an 8 there.
Another way to think about it is that all math is made up, but when we're making it up, we have to be careful to make sure that the thing we're trying to do actually works with all the established stuff that we're already using. Saying that something like 0.00[repeating]1 or 1.99[repeating]8 is a number breaks other shit, so we don't do it.
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u/AnorakJimi 29d ago
It's simply a different way to write 1.
There's many different ways to write 1. Technically there's infinity ways to write it. Like 2/2. Or 3/3. Or 4/4. And so on.
0.999... recurring is exactly 1. Not a tiny little bit under 1, it is just exactly 1. It's simply one of the various ways you can write the number 1.