• Pipoca@lemmy.world
    link
    fedilink
    arrow-up
    9
    ·
    11 months ago

    It’s BE(D=M)(A=S). Different places have slightly different acronyms - B for bracket vs P for parenthesis, for example.

    But multiplication and division are whichever comes first right to left in the expression, and likewise with subtraction.

    Although implicit multiplication is often treated as binding tighter than explicit. 1/2x is usually interpreted as 1/(2x), not (1/2)x.

    • CheesyFox@lemmy.world
      link
      fedilink
      arrow-up
      1
      ·
      11 months ago

      a fair point, but aren’t division and subtraction are non-communicative, hence both operands need to be evaluated first?

    • unoriginalsin@lemmy.world
      link
      fedilink
      Afaraf
      arrow-up
      1
      ·
      11 months ago

      It’s BE(D=M)(A=S). Different places have slightly different acronyms - B for bracket vs P for parenthesis, for example.

      But, since your rule has the D&M as well as the A&S in brackets does that mean your rule means you have to do D&M as well as the A&S in the formula before you do the exponents that are not in brackets?

      But seriously. Only grade school arithmetic textbooks have formulas written in this ambiguous manner. Real mathematicians write their formulas clearly so that there isn’t any ambiguity.

      • Pipoca@lemmy.world
        link
        fedilink
        arrow-up
        2
        ·
        edit-2
        11 months ago

        That’s not really true.

        You’ll regularly see textbooks where 3x/2y is written to mean 3x/(2y) rather than (3x/2)*y because they don’t want to format

        3x
        ----
        2y
        

        properly because that’s a terrible waste of space in many contexts.

              • Pipoca@lemmy.world
                link
                fedilink
                arrow-up
                1
                ·
                edit-2
                11 months ago

                Grade school is a US synonym for primary or elementary school; it doesn’t seem to be used as a term in England or Australia. Apparently, they’re often K-6 or K-8; my elementary school was K-4; some places have a middle school or junior high between grade school and high school.

                • unoriginalsin@lemmy.world
                  link
                  fedilink
                  Afaraf
                  arrow-up
                  1
                  ·
                  11 months ago

                  I don’t know why you’re getting lost on the pedantry of defining “grade school”, when I was clearly discussing the fact that you only see this kind of sloppy formula construction in arithmetic textbooks where students are learning the basics of how to perform the calculations. Once you get into applied mathematics and specialized fields that use actual mathematics, like engineering, chemistry and physics, you stop seeing this style of formula construction because the ambiguity of the terms leads directly to errors of interpretation.

                  • Pipoca@lemmy.world
                    link
                    fedilink
                    arrow-up
                    1
                    ·
                    11 months ago

                    Sure, the definition of grade school doesn’t really matter too much. Because college texts are written in ways that violate pemdas.

                    Look, for example, at https://www.feynmanlectures.caltech.edu/I_45.html

                    For example, if f(x,y)=x2+yx, then (∂f/∂x)y=2x+y, and (∂f/∂y)x=x. We can extend this idea to higher derivatives: ∂2f/∂y2 or ∂^2f/∂y∂x. The latter symbol indicates that we first differentiate f with respect to x, treating y as a constant, then differentiate the result with respect to y, treating x as a constant. The actual order of differentiation is immaterial: ∂2f/∂x∂y=∂2f/∂y∂x.

                    Notice: ∂^2f/∂y∂x is clearly written to mean ∂^2f/(∂y∂x).