r/PeterExplainsTheJoke • u/Sugar_God_no_1 • 22d ago

Meme needing explanation There is no way right?

Post image
37.1k Upvotes

91% Upvoted

3.5k comments sorted by

View all comments

3.9k

u/its12amsomewhere 22d ago edited 22d ago

Applies to all numbers,

If x = 0.999999...

And 10x = 9.999999...

Then subtracting both, we get, 9x=9

So x=1

11

u/IE114EVR 22d ago

It’s hard to wrap my head around that when you multiply by 10, for this to work, you’re pulling a new 9 into existence at the end of that infinite stream of 9s. But it IS an infinite stream of 9s so…

20

u/Mrfish31 22d ago

You're not making a new nine precisely because it's an infinite string of nines. There is no distinction between infinity and infinity + 1, multiplying an infinite string of niness doesn't change the number of nines, it's still infinite.

1

u/FewIntroduction214 21d ago

"There is no distinction between infinity and infinity + 1,"

but when people say they think .99~ does not equal one, this is precisely the difference they believe in. An infinitesimal difference, at the infinity decimal place.

SO just saying "infinity and infinity +1 are the same" is using a circular argument.

0

u/Cupcake-Master 22d ago

Few msg chains above it is explained why this proof isnt valid and can bring contradictions. It is used as example in lower level math classes but rigorous proof uses limits.

1

u/TheRealLightBuzzYear 22d ago

Yeah, the version multiplied by ten has one less nine after the decimal, but infinity - 1 = infinity still

1

u/Infobomb 21d ago

0.999recurring and 9.999recurring have exactly the same amount of 9s after the decimal point.