Comment on (I wonder if he knows about lemmy)1 divided by 0 (a 3rd grade teacher and principal got it wrong), Reddit r/NoStupidQuestions [4:51 | Dec 02 2023 | bprp precalculus]

• magic_lobster_party@kbin.social ⁨9⁩ ⁨months⁩ ago

  Quora has many dubious answers. I wouldn’t use it for any point of argument.

  Infinity is not a number. It’s a concept. You’ll find yourself in many paradoxes if you start treating infinity as a number (you can easily prove that 1 = 2 for example).

  By your argument, is 1/|x| negative infinity when x is 0? The expression is strictly positive, so it doesn’t make sense to assign it a negative value. But your version of infinity would make it both positive and negative.

  Another one: try to plot y = (x^2 - 1) * 1/(x - 1). What happens to y when x approaches 1? If you look at a plot, you’ll see that y actually approaches 2. What would happen if we treat 1/(1-1) as your version of infinity? Should we consider that y could also approach -2, even if it doesn’t make any sense in this context?

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  • doctorn@r.nf ⁨9⁩ ⁨months⁩ ago

    Curious I found something that proofs my whole point exactlybto the letter though… I must ge exactly the same kind of wrong as that other person that actually drew ypu the circle with it as proof…

    C’mon, now you’re just reaching.

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    • magic_lobster_party@kbin.social ⁨9⁩ ⁨months⁩ ago

      The circle is just a visualization of a concept, not a proof. The Quora answer clearly refers to this concept: https://mathworld.wolfram.com/ProjectivelyExtendedRealNumbers.html

      The page clearly states this is a non-standard number system. You cannot use it in the general case. It is a common practice for mathematicians to come up with new number systems with new rules and see where it leads to. Maybe there’s a practical use for it?

      This is the same case here. Some mathematician came up with a new number system where 1/0 is treated as a new number with special properties and see what it leads to. Any new conclusion made in this number system is probably not applicable in any standard number system.

      The article also mentions this number system: https://mathworld.wolfram.com/AffinelyExtendedRealNumbers.html

      Similarly this is a number system that has been constructed such that infinity exists as a number, but in this case negative infinity is a distinct number. 1/0 is not defined under this system as a result. This is a non-standard system as well, so shouldn’t be used unless it’s clearly intended.

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    • MacGuffin94@lemmy.world ⁨9⁩ ⁨months⁩ ago

      Dude you picked an obscure sub field of mathematics defined by looping a set around a sphere in order to make both positive and negative infinity equal. That’s like saying sea food is bad because I asked something allergic to shell fish if they like it.

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