this post was submitted on 07 Dec 2023
309 points (100.0% liked)
Asklemmy
1454 readers
60 users here now
A loosely moderated place to ask open-ended questions
Search asklemmy π
If your post meets the following criteria, it's welcome here!
- Open-ended question
- Not offensive: at this point, we do not have the bandwidth to moderate overtly political discussions. Assume best intent and be excellent to each other.
- Not regarding using or support for Lemmy: context, see the list of support communities and tools for finding communities below
- Not ad nauseam inducing: please make sure it is a question that would be new to most members
- An actual topic of discussion
Looking for support?
Looking for a community?
- Lemmyverse: community search
- sub.rehab: maps old subreddits to fediverse options, marks official as such
- !lemmy411@lemmy.ca: a community for finding communities
~Icon~ ~by~ ~@Double_A@discuss.tchncs.de~
founded 5 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Under normal interpretations of pemdas this is simply wrong, but it's ok. Left to right only applies very last, meaning the divisor operator must literally come after 2(4).
This isn't really one of the ambiguous ones but it's fair to consider it unclear.
Pemdas puts division and multiplication on the same level, so 34/22 is 12 not 3. Implicit multiplication is also multiplication. It's a question of convention, but by default, it's 16.
https://en.m.wikipedia.org/wiki/Order_of_operations
Incorrect, pemdas puts multiplication before division.
Only in the literaly order of the words.
It stands for "Parentheses, Exponents, Multiplication/Division, Addition/Subtraction"
Notice the "/" between multiplication and division instead of a comma? That means these have the same priority.
Well there's the problem. I maintain this to be a mistake.
Ok. You could also maintain that 1 + 1 equals 3 if you wish. Either way you are simply wrong.
I don't think you understand my position if that's your takeaway.
Your position is that you disagree with established maths. So you're kind of a maths-flatearther with your own theories, I get it. But for most people that just summarizes to "being wrong".
Huh? I disagree with the convention, not the underlying math. Pemdas is a design choice lol.
I always thought pemdas was more like P/E/MD/AS with MD and AS occurring left to right
This is how I was taught, but also people don't really use the Γ· symbol in algebra beyond like 6th grade
Yes they do, just pick up a high school Maths textbook (in a country which uses obelus rather than colon).
And "Multiplication" refers literally to multiplication signs, of which there are none in this question.
There's no such thing as implicit multiplication. The answer is 1.
I don't know what you're on about with your distributive law thing. That just states that
a*(b + c) = a*b + a*c, and has literally no relation to notation.And "math is never ambiguous" is a very bold claim, and certainly doesn't hold for mathematical notation. For some simple exanples, see here: https://math.stackexchange.com/questions/1024280/most-ambiguous-and-inconsistent-phrases-and-notations-in-maths#1024302
No, The Distributive Law states that a(b+c)=(ab+ac), and that you must expand before you simplify.
Examples by people who simply don't remember all the rules of Maths. Did you read the answers?
Please learn some math before making more blatantly incorrect statements. Quoting yourself as a source is... an interesting thing to do.
https://en.m.wikipedia.org/wiki/Distributive_property
I did read the answers, try doing that yourself.
I'm a Maths teacher - how about you?
I wasn't. I quoted Maths textbooks, and if you read further you'll find I also quoted historical Maths documents, as well as showed some proofs.
I didn't say the distributive property, I said The Distributive Law. The Distributive Law isn't ax(b+c)=ab+ac (2 terms), it's a(b+c)=(ab+ac) (1 term), but inaccuracies are to be expected, given that's a wikipedia article and not a Maths textbook.
I see people explaining how it's not ambiguous. Other people continuing to insist it is ambiguous doesn't mean it is.
If you read the wikipedia article, you would find it also stating the distributive law, literally in the first sentence, which is just that the distributive property holds for elemental algebra. This is something you learn in elementary school, I don't think you'd need any qualification besides that, but be assured that I am sufficiently qualified :)
By the way, Wikipedia is not intrinsically less accurate than maths textbooks. Wikipedia has mistakes, sure, but I've found enough mistakes (and had them corrected for further editions) in textbooks. Your textbooks are correct, but you are misunderstanding them. As previously mentioned, the distributive law is about an algebraic substitution, not a notational convention. Whether you write it as
a(b+c) = ab + acor asa*(b+c) = a*b + a*cis insubstantial....which isn't a Maths textbook!
Except what it states is the Distributive property, not The Distributive Law. If I call a Koala a Koala Bear, that doesn't mean it's a bear - it just means I used the wrong name. And again, not a Maths textbook - whoever wrote that demonstrably doesn't know the difference between the property and the law.
No it isn't. This is a year 7 topic. In Primary School they are only given bracketed terms without a coefficient (thus don't need to know The Distributive Law).
No, I'm not assured of that when you're quoting wikipedia instead of Maths textbooks, and don't know the difference between The Distributive Property and The Distributive Law, nor know which grade this is taught to.
BWAHAHAHAHA! You know how many wrong things I've seen in there? And I'm not even talking about Maths! Ever heard of edit wars? Whatever ends up on the page is whatever the admin believes. Wikipedia is "like an encyclopedia" in the same way that Madonna is like a virgin.
And yet you have failed to point out how/why/where. In all of your comments here, you haven't even addressed The Distributive Law at all.
And neither of those examples is about The Distributive Law - they are both to do with The Distributive Property (and you wrote the first one wrong anyway - it's a(b+c)=(ab+ac). Premature removal of brackets is how many people end up with the wrong answer).
Let me quote from the article:
"In mathematics, the distributive property of binary operations is a generalization of the distributive law, which asserts that the equality
x*(y+z) = x*y + x*zis always true in elementary algebra."This is the first sentence of the article, which clearly states that the distributive property is a generalization of the distributive law, which is then stated.
Make sure you can comprehend that before reading on.
To make your misunderstanding clear: You seem to be under the impression that the distributive law and distributive property are completely different statements, where the only difference in reality is that the distributive property is a property that some fields (or other structures with a pair of operations) may have, and the distributive law is the statement that common algebraic structures like the integers and the reals adhere to the distributive property.
I don't know which school you went to or teach at, but this certainly is not 7th year material.
Let me say again, people calling a Koala a Koala bear doesn't mean it actually is a bear. Stop reading wikipedia and pick up a Maths textbook.
It's not an impression, it's in Year 7 Maths textbooks.
And yet it appears in every Year 7 textbook I've ever seen.
Looks like we're done here.
If you don't want to see why you're wrong that's your thing, but I tried. I can just say, try to re-read the math textbook you took pictures of, and try to understand it.
About the ambiguity: If I write
f^{-1}(x), without context, you have literally no way of knowing whether I am talking about a multiplicative or a functional inverse, which means that it is ambiguous. It's correct notation in both cases, used since forever, but you need to explicitly disambiguate if you want to use it.I hope this helps you more than the stackexchange post?
The inverse of the function is f(x)^-1. i.e. the negative exponent applies to the whole function, not just the x (since f(x) is a single term).
You can define your notation that way if youlike to, doesn't change the fact that commonly
f^{-1}(x)is and has been used that way forever.If I read this somewhere, without knowing the conventions the author uses, it's ambiguous
Nothing to do with me - it's in Maths textbooks.
Well they should all be following the rules of Maths, without needing to have that stated.
Exactly! It's in math textbooks, in both ways! Ambiguous notation, one might say.
And both ways are explained, so not ambiguous which is which.
Yeah, doesn't mean that you know what an author is talking about when you encounter it doing actual math
The notation is not intrinsically clear, as any human writing. Ambiguous, one may say.
It is to me, I actually teach how to write it.
We've been at this point, I'm not going to explain this again. But you weren't able to read a single sentence of a wikipedia article without me handfeeding it to you, so I guess I shouldn't be surprised. I'm sorry for your students.
And I told you why it was wrong, which is why I read Maths textbooks and not wikipedia.
My students are doing good thanks
Apparently you can't read either textbooks or wikipedia and understand it.
Also, wait, you're just a tutor and not actually a teacher? Being wrong about some incredibly basic thing in your field is one thing, but lying about that is just disrespectful, especially since you drop that in basically every sentence.
Both - see the problem with the logic you use?
Let me know when you decide to consult a textbook about this.
I'm not using logic in this case, you are just being insincere. Let me know when you bother to try to understand anything I or the authors of your holy textbooks wrote.
That is incorrect. Multiplication does NOT have presedence of division, they are equal. So it's left to right, which means division comes first.
Which brings you to a yet further ambiguous expression. I maintain that's a poor choice.
#MathsIsNeverAmbiguous if you follow all the rules of Maths (there's a lot of people here who aren't).