this post was submitted on 02 Jul 2024
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chapotraphouse

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This little guy craves the light of knowledge and wants to know why 0.999... = 1. He wants rigour, but he does accept proofs starting with any sort of premise.

Enlighten him.

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[–] bestmiaou@lemmygrad.ml 9 points 4 months ago

so, start with:

x = 0.999...

now multiply each side by 10

10x = 9.9999....

now we subtract x from the left side, and 0.999... from the right, which is fine because they are equal:

9x = 9

and from there it should be fairly obvious that x is also equal to 1, which means 0.999... is also equal to 1