• @weastie
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    82 months ago

    Nope, you can’t assume the - is included in the square if there’s no parenthesis around it. The answer is -9. Think of it like “0-3²” which is more obviously -9.

    • flamingos-cantOP
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      2 months ago

      Nope, you can’t assume the - is included in the square if there’s no parenthesis around it. The answer is -9.

      Surely that would mean the answer’s ambiguous, no? The lack of brackets means we can’t know definitively if - is included or not. But separately, I’d argue that -3 represents negative three, not subtract three, and negative three is it’s own distinct number from positive three.

      • Surely that would mean the answer’s ambiguous, no?

        No. Exponents before Subtraction. Order of operations rules.

        The lack of brackets means we can’t know definitively if - is included or not

        The lack of brackets mean we definitively do know that it’s not included, because to be included, it would have to be in brackets.

        I’d argue that -3 represents negative three, not subtract three

        It’s actually 0-3. There’s an unwritten 0, just like if the first number was positive there’s an unwritten +. 9 is actually 0+9. All operations on the number line start from 0.

        negative three is it’s own distinct number from positive three

        “positive 3” is actually 0+3.

      • @[email protected]
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        2 months ago

        Perhaps it’s not the most clear, but that absolutely is the standard convention for how to treat exponents, because it results in much simpler shorthand for writing things like this:

        https://en.wikipedia.org/wiki/Taylor_series

        Example on that page:

        -x-(1/2)x^2 -(1/3)x^3 -(1/4)x^4 …

        Using your definition you’d have to put a bunch of parenthesis: -x-(1/2)(x^2 )-(1/3)(x^3 )-(1/4)(x^4 )…

        And believe me physicists would hate you if you made them do this because they’d have to do it constantly.

        • flamingos-cantOP
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          32 months ago

          It’s been a hot minute since I’ve had to do any serious maths, but that does roughly line up with what I remember about BODMAS. It’s just intuitively, there’s a difference between - as an infix operator (10 - 5) and - as a prefix (-3). If you where to solve x2 where x = -3, I don’t think you’d say it’s -9.

          • there’s a difference between - as an infix operator (10 - 5) and - as a prefix (-3).

            The only difference is whether it’s in brackets or not. To square the number -3 you need to put it in brackets, otherwise you’re only squaring 3.

            x2 where x = -3, I don’t think you’d say it’s -9

            That’s because anytime you substitute for a pronumeral, whatever the pronumeral represents goes in brackets. e.g. for x=3, 2x=2(3). So if x=-3, then x²=(-3)², as opposed to if x=3, we have -x²=-(3)². Whatever the pronumeral is equal to is inside brackets when you substitute.