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

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  • nandeEbisu@lemmy.ml
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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.ml
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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