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Joined 1 year ago
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Cake day: July 8th, 2023

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  • nandeEbisu@lemmy.mltoMemes@lemmy.mlNice
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    1 year ago

    Its not that there’s no definition for the notation, but if you fall back to commonly held definitions, there is divergence in common definitions without the parenthesis. Plenty of calculators, especially old ones, don’t respect PEMDAS, so the so by adding brackets your expression is going to fit the intended operations in more commonly used systems than had you left the brackets out.

    I also do think its a bit more readable as your eyes are initially drawn to the first operation, you can start evaluating expressions without even parsing the rest of the equation, or you can just block out that entire chunk when you start looking at how many terms are in the equation. That’s subjective though, so to each their own.


  • nandeEbisu@lemmy.mltoMemes@lemmy.mlNice
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    1 year ago

    I’m an engineering major, we learn all of the edge cases as “well technically this isn’t always true, but we’ll just pretend it is because the results are close enough”

    Every value of Y works for X=0, the equation simplifies to Y=Y, so X=0 is just like Y=9.

    In the limit as X->infinity, you get Y = 9 again.

    X(1+Y) + Y = 10*X + Y lim X->inf Assuming Y is finite, you drop the non-X terms

    X(1+Y) = 10*X lim x->inf

    Here, because X is non-zero and equal to itself, you can cancel them (I assume, IANA Mathematician) 1 + Y = 10 Y = 9






  • nandeEbisu@lemmy.mltoMemes@lemmy.mlNice
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    1 year ago

    Notation without a definition of what notation you’re using is always going to be ambiguous.

    If I wrote

    6 9 * 6 9 + +

    You wouldn’t know what that is, until I told you it was reverse polish notation, then you would know it resolves to 69 and does the same operations as the original equation.


  • nandeEbisu@lemmy.mltoMemes@lemmy.mlNice
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    1 year ago

    Huh, that’s true of any number that ends in 9.

    XY + X + Y = 10*X + Y

    Y’s cancel,

    XY = 9X => Y = 9 for any non-zero finite value of X.

    so for 69? X = 6, Y=9

    (6*9) + 6 + 9 = 10*6 + 9

    54 + 15 = 69

    69 = 69 (nice!)

    429? X = 42 Y = 9

    (42*9) + 42 + 9 =10*42 + 9

    (378) + 51 = 429

    429 = 429

    Even if 10X+Y doesn’t equal something that ends in 9 it works

    X=3.14 Y=9

    (3.14*9) + 3.14 + 9 = 10*3.14 + 9

    28.26 + 12.14 = 40.4

    40.4 = 40.4

    Doesn’t work if Y =\= 9:

    68? X = 6 Y = 8

    (6*8) + 6 + 8 ?= 10*6 + 8

    (48) + 14 ?= 68

    62 =\= 68