• etchinghillside@reddthat.com
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    3 hours ago

    It’s been a while… but isn’t that negative?

    Or is there some default given of which side it’s approaching from.

    • Sculptus Poe@lemmy.world
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      1 hour ago

      (Just including the graph for reference. I’m not sure it helps with proper description or the answer the teacher was asking for, but you can see that from one direction it goes negative as you approach 8 and from the other it goes to positive infinity.)

    • LeFrog@discuss.tchncs.de
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      3 hours ago

      I think it is not defined. It has a limes from the left (- inf) and limes from the right (+ inf) but no two-sided limes.

      Edit: wolframalpha agrees but I don’t know for sure

    • JustAPenguin@lemmy.world
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      2 hours ago

      I have a BA in Mathematics. The limit is indeed determined by the direction you approach the limiting value.

      When given without specification, the limit is implied to come from the left, meaning it increases towards the limiting value, which is why you see +inf.

      • rooroo@feddit.org
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        2 hours ago

        Yeah but then it should be negative infinite, cause if x<8 the fraction is negative.

        • JustAPenguin@lemmy.world
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          2 hours ago

          Ah, I misread the - as a +. You’re correct! Sorry, I just woke up and am in the middle of my morning doomscrolling sesh

          • deadbeef79000@lemmy.nz
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            19 minutes ago

            Conveniently modeled with the same limit.

            Though I’m not sure what negative doom is and what happens when it approaches infinity.

  • jjj@lemmy.blahaj.zone
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    2 hours ago

    The first one is incorrect, the limit doesn’t exist unless you specify whether you’re coming from the left or right.

    On another note, I think their student has invented a new symbol for “Does Not Exist”.

  • webghost0101@sopuli.xyz
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    2 hours ago

    Story time, third grader me would have done this no questions about it.

    Having to solve multiplication and recently had learned the table of 9 trick i was looking if there where other tricks I could find.

    The first one was number x10 and what i observed is that if you do times ten. You take the number. And you put 1 “0” behind it.

    Interesting…. I thought

    But the next one multiplied with a single digit so how could i apply that theory.

    Simple. 1+0 is 1, which is a single digit so if you multiply by 10, you actually multiply by 1+0 which means you put 1 zeros behind it

    Multiple by 2 is short for multiply By 2+0, put 2 zeros behind it

    Multiply by 9, put 9 zeros behind it.

    I definitely knew this is not what we had learned, and knew there was a “chance” i was going to fail all of these, i also even knew some of the actual answers however i also believed there was a chance that i found an alternative equally good solution, and I consciously decided to take that risk because I wanted to know if i was right. Maybe I discovered something new

    My teacher was not happy to say the least, and in that (actual) furry did treat me unfair and it still bothers me. Because i got a zero for the assignment… while i was very certain that the 2 occurrences of x10 did have the appropriate solution.