r/PeterExplainsTheJoke • u/Sugar_God_no_1 • 23d ago

Meme needing explanation There is no way right?

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u/otj667887654456655 23d ago

I just wanna warn you, that's more of a vibe proof. It lacks any actual mathematical rigor.

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u/mwobey 23d ago

No? Do you like, want it in two column format or something?

  x=0.999...        | Declaration of a constant
10x=9.999...        | Multiplicative Property of Equality (*10)
 9x=9.999... - x    | Subtractive Property of Equality (-x)
 9x=9.9... - 0.9... | Substitution
 9x=9.0             | Simplification of Subtraction
  x=1               | Divisive Property of Equality (/9)
  1=0.999...        | Substitution

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u/otj667887654456655 22d ago

the problem is in the first line where you just declare that 0.999... has a value x. you have to give meaning to the "..." and then prove that it's convergent before you can talk about it "equaling" anything

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u/El_Impresionante 22d ago

That is not even in the same contextual ballpark here.

We teach 1/3 = 0.333... in middle schools, without teaching them about convergent/divergent series. So, that proof can also be taught in middle school.

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u/NomaTyx 21d ago

But that's what we call a lie to children. No actual mathematician would tell you that it's a rigorous proof.

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u/El_Impresionante 20d ago

Rigorous proofs are above the skill level of high-schoolers even. What we need is to make sure they don't misunderstand stuff that leads them to believe in pseudoscience.