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Intermediate Algebra

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Re: Intermediate Algebra

#21
post #6
post #4

Earlier quoted context omitted.

I think it’s clear you’ve never taught low level mathematics courses. There is a lot of hand waving and brain washing that happens. The vast majority of people don’t know what a number is in a precise, mathematical sense. At the level of the intended audience it would be wholly inappropriate talk about the definition of a number. My background on this topic is that I’ve taught intermediate algebra for over 20 years.

You are right, I didn't teach low level math courses, but this brain washing is also precisely why I didn't understand math in high school. You cannot argue with this kind of definitions. Everything feels as if it was randomly defined by the teacher. This "intuition" simplifies teaching, but makes understanding harder. It is like a game where you invent rules as you play. No student can win this game.

You "win at the game" by learning what is taught, getting the "A", and then doing you own in-depth research about what interests you on your own time.

K-12 was, of course, invented by the Germans in order to create good little factory workers that would get up early and work all day and not complain too much. The fact we still use the word Kindergarten is a nod to this origin story.

They weren't at all interested in the students gaining any "understanding" and most certainly not in them "winning" in any sense of the word.

Re: Intermediate Algebra

#22
post #17
post #9

Earlier quoted context omitted.

I'm completely serious here. Could you give us your definition of "number" which you would teach at this level? Please, please, I'm not trying to be an ass or anything. We could start a great conversation here.

I'm sure there are more elegant approaches, but I would start like this: A number is an imaginary (as in made up by humans, not as in complex numbers) object that solves certain equations. It is not well defined and should not be used as basis for other definitions. "Natural numbers" can be constructed directly and have a well known notation. Integer numbers are used to make the equation "a + x = b" solvable by x for…

Personally I find these definitions a bit circular.

Equations like "a + x = b", "ax = b" and "sin(x) = 0" have no meaning unless you have an understanding of what the terms mean, or could mean.

Re: Intermediate Algebra

#23
post #17
post #9

Earlier quoted context omitted.

I'm completely serious here. Could you give us your definition of "number" which you would teach at this level? Please, please, I'm not trying to be an ass or anything. We could start a great conversation here.

I'm sure there are more elegant approaches, but I would start like this: A number is an imaginary (as in made up by humans, not as in complex numbers) object that solves certain equations. It is not well defined and should not be used as basis for other definitions. "Natural numbers" can be constructed directly and have a well known notation. Integer numbers are used to make the equation "a + x = b" solvable by x for…

>A number is an imaginary object

and now the time has come for Intro to Complex Analysis, good luck not leaving everyone completely dumbfounded.

Re: Intermediate Algebra

#24
post #17
post #9

Earlier quoted context omitted.

I'm completely serious here. Could you give us your definition of "number" which you would teach at this level? Please, please, I'm not trying to be an ass or anything. We could start a great conversation here.

I'm sure there are more elegant approaches, but I would start like this: A number is an imaginary (as in made up by humans, not as in complex numbers) object that solves certain equations. It is not well defined and should not be used as basis for other definitions. "Natural numbers" can be constructed directly and have a well known notation. Integer numbers are used to make the equation "a + x = b" solvable by x for…

[deleted]

Re: Intermediate Algebra

#25
post #19

Earlier quoted context omitted.

This volume does not confuse R as the algebraic completion of Q. It is completely reasonable for an Algebra 1/2 teacher to wait for a Calculus or Analysis teacher to discuss the metric completion of Q. Describing R as rational + irrational numbers is a completely solid description.

It is only solid as long as you don't define irrational numbers literally as everything that is not rational.

What would be an example of a real number that's neither rational nor irrational? (I'm not a math guy, in case it's not obvious)

Re: Intermediate Algebra

#26
post #20

Earlier quoted context omitted.

If we're talking about "number" in general, yes, it is true that this is an informal term among mathematicians.

What mathematicians are you talking about? Set theorists and number theoriests have very precise definitions of numbers. Maybe by "number" in general do you mean something that encapsulates both "real numbers" as in lengths, and "integers" as in the discrete counting numbers? In which you can quite easily do so by defining real numbers, either formally or saying that something like the Wikipedia definition that they…

[deleted]

Re: Intermediate Algebra

#27
post #22
post #17

Earlier quoted context omitted.

I'm sure there are more elegant approaches, but I would start like this: A number is an imaginary (as in made up by humans, not as in complex numbers) object that solves certain equations. It is not well defined and should not be used as basis for other definitions. "Natural numbers" can be constructed directly and have a well known notation. Integer numbers are used to make the equation "a + x = b" solvable by x for…

Personally I find these definitions a bit circular. Equations like "a + x = b", "ax = b" and "sin(x) = 0" have no meaning unless you have an understanding of what the terms mean, or could mean.

You can easily define + on natural numbers and * on integer numbers without running into problems! Thus there is no cirularity here.

Re: Intermediate Algebra

#28
post #17
post #9

Earlier quoted context omitted.

I'm completely serious here. Could you give us your definition of "number" which you would teach at this level? Please, please, I'm not trying to be an ass or anything. We could start a great conversation here.

I'm sure there are more elegant approaches, but I would start like this: A number is an imaginary (as in made up by humans, not as in complex numbers) object that solves certain equations. It is not well defined and should not be used as basis for other definitions. "Natural numbers" can be constructed directly and have a well known notation. Integer numbers are used to make the equation "a + x = b" solvable by x for…

> A number is an imaginary object that solves certain equations.

TBH this is the worst explanation of anything I have ever seen.

Re: Intermediate Algebra

#29
post #19

Earlier quoted context omitted.

This volume does not confuse R as the algebraic completion of Q. It is completely reasonable for an Algebra 1/2 teacher to wait for a Calculus or Analysis teacher to discuss the metric completion of Q. Describing R as rational + irrational numbers is a completely solid description.

It is only solid as long as you don't define irrational numbers literally as everything that is not rational.

i or some hyper real numbers are neither irrational nor rational. Basically all crazy extensions of R used to solve even more crazy problems. They don't really exist naturally (and you can make up your own field extension of R as you wish), but they are handy if you want to compute stuff.

But by definition there are no real numbers that are neither rational or irrational.

Re: Intermediate Algebra

#30
post #4

Earlier quoted context omitted.

I think it’s clear you’ve never taught low level mathematics courses. There is a lot of hand waving and brain washing that happens. The vast majority of people don’t know what a number is in a precise, mathematical sense. At the level of the intended audience it would be wholly inappropriate talk about the definition of a number. My background on this topic is that I’ve taught intermediate algebra for over 20 years.

What should I read if I want to learn what a number is?

I'll preface this by saying that I got bored and didn't finish it (Axioms? Rubbish, where's my field theory etc.) but Terence Tao's book on Algebra seemed like a somewhat gentle and very thoughtful introduction to the subject. Not necessarily easy by any means but it looks like he has put a lot of work into the pedagogy (whereas some mathematicians just shit out theorem and proof onto the page with no regard whatsoever for the prose, justification or flow - but I (am forced to) digest)
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