Ask MetaFilter questions tagged with algebra

y = mx + b. Etc.

dfriedman — Sat, 07 Nov 2009 08:54:39 -0800

So I'm tutoring my cousin in algebra. Specifically, 9th grade algebra. Even more specifically, in preparation for the New York State Regents test in algebra. I'm 20 years older than he, and always found algebra pretty easy and straightforward. What tips do you have for a 34 year old tutor to a 14 year old who is struggling with algebra?

Hopelessly lost in algebra land

hollygoheavy — Mon, 05 Oct 2009 06:40:28 -0800

I am having the hardest time working with positive and negative integers in elementary algebra. Please hope me. I'm back in college after 20+ years and have gone back in time to elementary algebra. I didn't get it in high school and I'm still having a hard time getting it now. My specific problem is adding and subtracting positive and negative numbers, as well as accurately reading them in an equation. For example:

5(-2) - 4(-2) + 3

this has my eyes crossed. I want to rewrite it as -10 - 8 + 3 which is I'm pretty sure incorrect. I have to get this straight now because otherwise I'll be making sign errors all through the rest of my class, even if my math and rest of the problem solving is correct.

I have made flash cards with the "rules" for addition and subtraction with signed integers and refer to them but sometimes I still come out with the wrong answer.

Does anyone have any other ideas or tips for how to get over this mental block I have with the whole signed integer thing?

Me Bad At ++

arniec — Fri, 02 Oct 2009 09:08:19 -0800

Not Homework Filter! Paypal Filter: Paypal charges me 2.9% plus $0.30 for every transaction. Someone needs to pay me X. What is the formula to determine how much they need to send with paypal so I get X and not X - (X * 0.029) - 0.30? This has frustrated me... I do favors for friends and they want to pay with the convenience of Paypal... but I can't figure out the formula to quickly determine how much they need to pay me. I end up spreadsheeting it and plugging in numbers until they match...

Say they owe me $100, I can't say $102.90 (which is 2.9% added to the $100) because 2.9% of $102.90 is higher than 2.9% of $100...

I guess I FAIL at Algebra today...

Bonus points if you show me HOW to calculate this so I'm learning something as well as the formula for how to do it. I mean, I have

X + (X * 0.029) + 0.3 = y

where X is what they owe me and Y is how much they have to pay Paypal so I get paid in full... But then I do all those algebra tricks, divide by X, etc. but haven't gotten it yet

Is there a simple computer program I can use to graph functions?

junipero — Tue, 15 Sep 2009 13:44:33 -0800

Is there an easy-to-use computer program (other than TI Interactive) I can use to draw graphs of functions when I'm writing my Algebra 2 tests? Ideally, I'd like to be able to easily graph functions (single functions as well as piecewise functions), save the graphs, and insert them into a Word document. I'm using Windows Vista.

I loved TI Interactive but for reasons I'm not entirely clear about my school did not renew our subscription to that program this year (I don't know if there is a compatibility issue with Vista or if there is some other reason they did not renew, but the bottom line is I can't use that program any more). I'd like to find something similar to TI Interactive, preferably something that is free or very cheap.

Algebra help with roots

dbooster — Wed, 10 Jun 2009 04:32:54 -0800

I need help with a math problem my sister-in-law has for homework. It involves adding and multiplying roots and it's been long enough since college that I don't quite remember how to do that. The question is: 3sq(5)[2sq(5)-5]. I did it two different ways, getting 15sq(5) once and 9sq(5) the next. Is either right? An answer would be appreciated and, moreover, an explanation as to how to do it. Thanks!

Math basics need be strengthening

JoeXIII007 — Wed, 11 Feb 2009 13:20:30 -0800

In need of some daily source of random math problems (upto basic calculus) that will reinforce or (if necessary) re-establish some real fundamental concepts in the algebra portions of calculus, unless something else might work. So I got my first exam back from 2nd Semester Calc based physics today and discovered I received a 78/100, which frankly is not bad compared to the average in the class (mid 60s) but still not great.

My problems were rooted in basic algebra that comes with methods of calculus, and even some elementary stuff as well. One example being I forgot to leave some variables alone in doing partial differentiation (w.r.t. z: 3yz^2 I took to 6z instead of 6yz OR w.r.t. y: 2y^2z^2 I took to 4yz instead of 4yz^2).

Another problem I ran into was that I took 10^-5 to be like 10E-5 on a regular calculator, which among a mess of scientific numbers could be a bad habit.

This has been a recurring problem over the years, but thanks to mercy of professors here and there, it has not been a problem as far as grading is concerned. Now that I have a pretty 'traditional' professor in the sense he will not accept such errors or weigh more heavily on concept, and seeing that I will be transferring into the Big Ten pretty soon, I need to correct this sooner rather than later.

So basically, a full daily workout of fundamentals covering a wide range of material would be in order, and preferably something that does not take too much time.

Unless there is some other thing worth looking into...? I mean I could just remind myself not to do that again, but I think I have been there before. Some reconfig is in need. Somehow. Even some simple daily physics probs might do the trick.

(RSS, if possible, is preferred)

Algebra tutor for placement test in the LA area

Kimberly — Wed, 07 Jan 2009 14:33:30 -0800

I have a friend who is looking for an algebra tutor in the Los Angeles area. Anyone have experience with one or know how to find one? She needs to know what to expect in terms of price and recommendations on how to find someone.

From my friend:

I'm looking for someone who can basically work with me for a couple of
days a week for few weeks to do a quick review of college algebra. I
was doing trig and calculus in high school, so it's not like I'm bad
with math -- it's just that high school was almost 15 years ago and
I'm really, really rusty.

Maximizing a function over orthogonal matrices

a robot made out of meat — Sun, 26 Oct 2008 08:26:48 -0800

Maximizing a function over orthogonal matrices, or: solving polynomial order 2 systems. Help me out or point me to a better forum / listhost. I have a function f(T) of a matrix that I want to maximize, which is order two in the elements of T. Easy, partial derivatives gives you a linear system. Here's the catch; I also want T to be orthonormal (the dot product of the rows to be zero or one -- the extension of orthogonal to non-square matrices).

The obvious way to maximize a function with constraints is to tack on Lagrange multipliers g(T) = f(T) + sum{lambda[ij](Ti . Tj - delta(i,j) ) }, but now g(T) is order three in parameters, and partial derivatives are order two and I don't know how to solve that system generally.

The dimension of T can be huge, tens of thousands. Let's not suggest numerics unless there's an amazing trick to deal with the dimensionality.

Any ideas? Maximization subject to orthogonality seems like something that should have come up a lot and someone have figured out.

How to use algebra to solve web design grid issue?

fauxtoes — Thu, 23 Oct 2008 06:56:39 -0800

I have a super-complicated algebraic equation I (somehow) developed as the solution to developing appropriate grid-based web design that has me completely stumped... The kicker here is that I need to use existing chunks of content with predefined widths of 680px wide, and 512px wide. I want a grid of equal columns and gutters that would accommodate both dimensions. To the best of my abilities, I've defined the problem as such:

(x*a) + ((x-1)*b) = 512
(y*a) + ((y-1)*b) = 680

where:

a= # of columns
b= # of gutters

x and y are simply the number of columns and gutters needed for each width.

Is this even solvable?

How can I rotate around 3 axes in opengl?

mebibyte — Tue, 14 Oct 2008 14:17:37 -0800

Please help me wrap my head around this 3d graphics math. :( I'm writing an application in OpenGL for learning purposes and I'm trying to allow the user to modify the angle by which I rotate an object around the X axis, the Y axis, and the Z axis.

My problem is that I only know how to do the following:

glRotatef(xAngle,1,0,0);
glRotatef(yAngle,0,1,0);
glRotatef(zAngle,0,0,1);

(basically, rotate around the x axis, then around the y axis, then around the z axis)

This doesn't work because, essentially, after rotating, say, 90 degrees about the x-axis, the y and z axes are no longer where they used to be. See this crude picture for more information on what I'm talking about.

What I'm looking for is best practice on what to do in this situation. I have two opengl books and I've searched the internet and I haven't been able to find out anything about this. Surely this must be a common problem?

Code or (well-explained, not dry) math theory would be much appreciated. Thanks!

Help me do sums.

Mwongozi — Wed, 24 Sep 2008 08:17:04 -0800

Stupidly simple math question. X = A + B
Y = C + B

Assuming you know X and Y, is it possible to determine the values for A, B, and C?

If not, which values can you determine?

Help me relearn mathematics and its practica applications

dcbarker — Fri, 01 Aug 2008 05:19:32 -0800

Applied Math Filter: Help me use math! I'd like to learn more about mathematics and it's practical applications - particularly in Computer Science I'm a Computer Networking graduate (under 25) who never really done much math at university. My course was somewhere between computer science and communications engineering so maths sort of slipped through the cracks.

Now, I'm looking to re-learn math. I know that a lot of mathematics is abstract but I'm having difficulties seeing practical applications.

Where I'm at:
I took calculus at high school but just scraped through (I spent more time fighting with the teacher than learning). I don't remember a bit of it. I'm pretty much at "square one" so will be learning from the start. I consider myself a quick learner in most areas but had a horrible foundation in math so never picked it back up. I've bought a couple of math books which should teach me the theory I need. I've always thought graphing calculators were pretty interesting but lack the mathematical knowledge to necessitate their use (or purchase). I'm currently in the process of ditching my "college job" to go for a "real job".

What I want:
I want to learn math with a view to using it practically (preferably in computer science).

How you can help:
I'd like suggestions on how I should go about learning mathematics and its practical applications. Which areas should I look at if I want to use mathematics in computing? I think my problem is that I can't see a practical application for math that I'd like to explore but I have a strong urge to develop my mathematics skills.

Any help would be greatly appreciated! Thanks!

Help me get my math on

baphomet — Tue, 17 Jun 2008 08:09:27 -0800

I need to brush up on my basic college math skills for a course readiness assessment in a week. What are some good resources online and what should I focus on? I'm going back to school in the fall and have my math course readiness assessment in a week. Unfortunately the last time I took a math class was in high school in 2001, and it was never my strong suit to begin with. I'm thinking that the degree I'm going to pursue (BA in Geography) is going to require basic math skills, and I have to complete at least one college-level math course to graduate anyway.

At this point my math skills are extremely rusty- things like FOIL, order of operations, etc, are all in the dusty nether-reaches of the stuff I forced out of my brain after high school. I know this is really basic stuff I learned in 7th or 8th grade, so it's kind of embarrassing to admit that I couldn't simplify to save my life, but there you have it.

I'm not looking for any advanced placement- I know that I'll need to take a basic college algebra class. That said, my fear is that I'll place below those courses and in the realm of courses that I'll need to pass- and pay for- but not receive college credit for before I can take algebra. I'm confident in my ability to catch up and re-learn this material, but what are some good resources to help me along with that?

Algebra for Social Scientists

Proginoskes — Sun, 30 Mar 2008 19:33:35 -0800

I tutor several people in a "Mathematics for the Social Sciences" course at a local university. This semester the material is focused on matrix algebra. For the most part, they have no trouble wrapping their heads around the notions of basic vector operations, row reduction, systems of equations, inverse matrices and determinants. But, they have a lot of problems with more abstract concepts such as linear independence, subspaces, basis and dimension. I'm wondering if anyone has any tips on helping them visualize and understand these ideas more clearly.

Tally of cycle types in a permutation group

Wolfdog — Sun, 09 Mar 2008 09:20:17 -0800

Anyone good with GAP? I've defined a largish permutation group and would like to make a tally of elements by cycle type - how many of each cycle type occurs in the group. Possible? Trivial? Use something else instead? Oh, and where's the right place to ask GAP questions?

Color algebra: How do I pick a color F will make known color C against known background B at opacity N?

weston — Mon, 18 Feb 2008 16:39:31 -0800

Color algebra: Given a color C, how do I pick a color F that will be color C when against background color B at opacity N? How would I do the same thing for a color multiplication? I'm guessing one can start by treating each color as an RGB or CMYK vector, but I'm more than a little fuzzy on exactly what these operations mean and therefore how to invert them to pick F.

If context matters in defining the operations, practically I'm concerned with whatever Illustrator CS and Fireworks 8 mean by the terms, but I'm interested in general observations as well.

Algebraic retard -- no law school 4 u?

aleahey — Mon, 26 Nov 2007 15:55:23 -0800

Algebra moron -- wants to go to law school? So I recently re-enrolled in a 2 year college, hoping to get a decent GPA and transfer to a real school. So far 4.0 GPA in everything but Algebra. I am. an algebraic. retard.

So my question is, are my chances at getting in to a good law school dashed? Has anyone passed the bar as algebraically challenged as I?

Please, only answers from people in the know, I don't need guesses.

Thanks :)

Make a function of this graph. That's like an anti-graph!

hammerthyme — Thu, 22 Nov 2007 09:24:14 -0800

Help me create a function from a graph, details inside. I want to create a function from this xkcd webcomic that depicts the so-called Ballmer Peak. To make it simple, I want the y-axis to peak at 10. Get out your calculators!

My head's about to explode...

Zé Pequeno — Sun, 28 Oct 2007 17:20:43 -0800

Can someone please point me in the right direction to find practice test papers for Financial Accounting? (Balance Sheets, Income Statements, Statements of Returns on Equity, Cash Flow Statements, Depreciation, Ratios, etc. etc.) Assorted business schools worries inside. Coming from a liberal arts academic background, I'm starting to really feel the pressure from my recently-started international business masters and get the impression I need to study ten times as hard as my classmates, most of whom have studied the subject at undergraduate level. At the moment, I'm fretting over Financial Accounting. Please help me to understand this subject!

Extra points for whoever can help me with Corporate Finance...

I was never strong at mathematics in school. Though I'm pretty good at mental arithmetic, I found the subject boring and didn't pay attention in class. Now I'm faced with the daunting task of getting to grips with Corporate Finance and have some decent books to help me, all of which cheerfully claim that the author needs no prior knowledge of Finance, just a knowledge of algebra! At the risk of appearing extremely dumb... I can't remember any algebra! What do I need to learn in order to understand the nimiety of equations by which I'm beginning to feel very overwhelmed?

How to write a mathematics paper

rolypolyman — Mon, 18 Jun 2007 17:47:38 -0800

I need to write a document with a lot of algebraic formulas. What word processor / page layout program would make this quickest and easiest? I use Windows, and have available Word, OpenOffice, PageMaker 7.0, and InDesign CS2 (whether it's layout or word processor software is not a big deal). I'd like to be able to set algebraic equations quickly and with minimum fuss so I can concentrate on the flow and writing (square roots, fractions, etc).

I know LaTeX (protext?) is often recommended for math, but I am worried about overkill and a steep learning curve. I'm not typesetting a calculus textbook or anything like that.

I am most used to PageMaker, but it has laughable math support. I considered finding a utility that creates a formula and spits out a TIF to embed in the document, but I nixed it as it could get excessively time consuming.

What would work best? I can consider cheap shareware or freeware (this is not for a professional project).

Self-teaching algebra

rolypolyman — Wed, 21 Feb 2007 11:34:13 -0800

I'm looking for textbook suggestions for teaching myself algebra and trigonometry. Are there any algebra textbooks that stand out as exceptionally good? The purpose of this is to augment my own scientific consulting and programming work, where math fluency will help "broaden my horizons", so I'm committed to learning math over the long term. I know I can just take a class, but the nearest university is 60 miles away and I have a toddler in the house, so it's not practical to take courses. Nor do I want to sit on my thumbs. Besides, I'm very self-motivated and like working at my own pace. I want to spend an hour a day in my den working on my math skills from the ground floor up. My wife has a science degree and was a math minor, so I have help around when I get stuck.

I am shaky in algebra and haven't been in a trig class in 21 years. I am committed to relearning algebra up through trig so that I can eventually tackle calculus months or years from now. I've got Algebra and Trigonometry (good; Addison-Wesley; Keedy, Bittinger & Beecher) and College Algebra (not bad; Harper-Collins; Orr), but maybe I can do better.

The ideal textbook would have lots of narrative without being dry and crusty, plenty of examples, and lots of problems with ALL of the solutions in the back. I hope I'm not asking too much of a book.

Typesetting a formula

chef_boyardee — Thu, 31 Aug 2006 16:21:42 -0800

Where can I find typographic conventions for algebra? Specifically... Here are two questions:

(1) Say just hypothetically that the number of people now (n) at 0 hours is the sum of the number of people (n) 12 hours ago and twice the number of people 24 hours ago. From what I can tell, I typeset the formula like this:

n = n₁₂ + 2n₂₄

As you can see, the 2 multiplier is nonitalicized, I italicized n, but left the subscripts nonitalicized. A book I have has them that way. Is that right?

(2) How do you handle a special category of number, for instance, the number of people (n) in the bathroom (b), say n_b. Would the number of people in the bathroom 24 hours ago be n_b24? Or should I invent a different variable, such as b?

Can ya help me be geeker?

horseblind — Sun, 23 Jul 2006 18:34:12 -0800

Can you help me with my innumeracy? Okay, innumeracy might be a bit of an overstatement. Here's the scoop. I'm very interested in mathematics but due to lack of real-world need I find that I don't know as much as I'd like to know from the world of math. Things I'd like to learn about are Algebra, Calculus, Number Systems, and how to think mathematically in general.

What do I hope to achieve with this new found mathematical thinking? I want to better understand some of the very questions posted here on AskMeFi. I want to read "Godel Escher Bach" with a better understanding and appreciation. I want to be able to increase the speed of the types of problems I can already resolve whther they are on paper or in my head. I want to have more fun with numbers.

I am in my mid-thirties and have had little mathematical need or education since highschool. I have no problems actually figuring things out but am submitting to the MeFi collective to give me a jump start. I currenty have little mathematical need, but this is rather about desire instead.

Please suggest books, websites, puzzlebooks or any other source that may help me better my own mathematical thinking.

The geek in me want to be geeker.

Practical math

Mwongozi — Wed, 28 Jun 2006 03:46:41 -0800

Math help. (Practical, I'm not in school!) n = xy

a = x/y

If I know the values of "n" and "a", can I calculate what x and y are?

How to teach a 14 year old girl algebra?

orthogonality — Sun, 26 Jun 2005 17:00:51 -0800

I need to teach a 14 year old girl algebra. How do I make it something that she actually wants to learn? And where can I find related free resources on the web? What's the most effective way to go about this?