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657942 Posts in 9260 Topics by 3396 Members Latest Member: - vlozan86 Most online today: 83 - most online ever: 494 (Jul 01, 2007, 02:59:53 PM)
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Author Topic: The concept of the variable / Can take it in the dumper (Algebra questions)  (Read 4174 times)
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elpollodiablo
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Posts: 32624


« on: Jul 22, 2008, 05:18:58 PM »

This is embarrassing, but I am deathly fucking terrified of not passing this class, and since I have to work all week, I don't have time to go to a tutor. So!

Can someone explain to me, in practical terms, how I can expand this:

(1-x)(1+2^2)^2

into this:

-x^5+x^4-2x^3+2x^2-x+1

?


Even telling me how exactly


(1-x)(1+2^2)^2

becomes

(1-x)(1+2x^2+x^4)

would get me off in the right direction. The book has been no help, it basically just says "Expand and collect like terms." FOILing it doesn't work, or if it does, I'm doing it wrong. The technique of vertical multiplication which has been so useful expanding factors in the past doesn't work, I'm guessing because of that second power of 2.

Please help!

Much Love
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elpollodiablo
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Posts: 32624


« Reply #1 on: Jul 22, 2008, 05:46:37 PM »

Bethany, thanks! You are teh awesome


I can't wait until I don't have to do algebra anymore. Fortunately, that'll be any time after this Friday! Razz

Unfortunately, if I don't do it at least skewing well on Friday, I have to do it for five more weeks at an exorbitant cost and maybe not move to NYC. Boo!
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bn
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Posts: 2


« Reply #2 on: Jul 22, 2008, 06:28:42 PM »

hi
i'm bethany's boyfriend.

um. so you were right to FOIL the equation to expand it out, but i think what you typed had a typo in it:
(1-x)(1+x^2)^2
=(1-x)(1+x^2)(1+x^2)
=(1-x)(1+2*x^2 +x^4)
=1+ 2*x^2+ x^4 -x -2x^3  -x^5
=-x^5 +x^4 -2 x^3 +2x^2 -x +1
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Andrew_TSKS
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Posts: 39426


« Reply #3 on: Jul 22, 2008, 06:46:45 PM »

Oh wow. I think I could have understood that in ninth grade, but as it is my head just exploded.
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YojimboMonkey
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Posts: 12034


« Reply #4 on: Jul 22, 2008, 07:10:43 PM »

Yeah I looked at that and thought he might have typed in the problem wrong, but I was working and didn't have the time to figure out what should have been there instead, so I'm glad we got a real mathematician dude up in here. Smile
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elpollodiablo
Registered user

Posts: 32624


« Reply #5 on: Jul 22, 2008, 07:16:18 PM »

Hi bn! Thanks so much for taking the trouble to register and come on here and help out! Your answer actually got me a little further; I'm just having trouble at the step indicated below:

(1-x)(1+x^2)^2
=(1-x)(1+x^2)(1+x^2)
=(1-x)(1+2*x^2 +x^4)
|
v
-->=1+ 2*x^2+ x^4 -x -2x^3  -x^5<--

=-x^5 +x^4 -2 x^3 +2x^2 -x +1

Just having trouble seeing how the third becomes the fourth... Dunno if you'll stick around for a follow up or not (you should; we're good people!), but if anyone could like assume that I am such as a fool when it comes to matters of numbers and explain it in baby steps, I'd be in your debt!
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heather marie
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Posts: 5753


« Reply #6 on: Jul 22, 2008, 07:22:15 PM »

Wow, I suck at Algebra when it is typed out on a computer. Regardless, bethany's boyfriend should become my new math tutor. Is taking Statistics online going to kill me this fall? I think it just might.
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YojimboMonkey
Registered user

Posts: 12034


« Reply #7 on: Jul 22, 2008, 07:24:59 PM »

well it's just that FOIL operation again

First you multiply the first term in the first parentheses by all the terms in the 2nd parentheses
1*1=1
1*2x^2=2x^2
1*x^4=x^4
So you end up with 1+2x^2+x^4

Then the second term in the first parentheses by all the terms in the 2nd parentheses
-x*1=-x
-x*2x^2=-2x^3
-x*x^4=-x^5
So you end up with -x-2x^3-x^5

Then you combine those terms

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alex
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Posts: 6287


« Reply #8 on: Jul 22, 2008, 07:28:55 PM »

(x-post with a person who actually knows maths, but I'll leave it in because it is even tinier baby steps. edit: nah, it's actually pretty much the same thing, but there you are.)

Miles - not sure if this is going to help, but what you have to do is to simply multiply each element of the first bracket with each element of the second bracket. Thus, for

=(1-x)(1+2*x^2 +x^4)

to become

=1+ 2*x^2+ x^4 -x -2x^3  -x^5

you have to first multiply everything in the second bracket with 1, and then substract everything in the second bracket multiplied by x. Thus:

1*1=1
1*2*x^2=2*x^2
1*x^4=x^4

and then you add the second element=
-x*1=-x
-x*2*x^2=-2*x^3
-x*x^4=-x^5

And that's all there is, as far as I can see.
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alex
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Posts: 6287


« Reply #9 on: Jul 22, 2008, 07:33:27 PM »

Wow, I suck at Algebra when it is typed out on a computer.

Yeah, I totally had to scribble this down on a piece of paper to figure out what you guys are even trying to accomplish here. Then once I did that, it all made perfect sense.

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elpollodiablo
Registered user

Posts: 32624


« Reply #10 on: Jul 22, 2008, 07:46:31 PM »

Wow, thanks a lot guys! I'm gonna print this out and see if I can force it into my brain.


This is so ridiculously hard trying to teach myself with a book and the internet, seriously
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elpollodiablo
Registered user

Posts: 32624


« Reply #11 on: Jul 22, 2008, 07:58:23 PM »

Man, THANK you guys so much! I swear ta christ I've been staring at that, trying different ways of coming at it, for two hours. I know that'll probably make some of ya chuckle, but I've basically foregone all dignity in favor of assistance.

If I get stuck on anything else, I'll post! Much Love
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heather marie
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Posts: 5753


« Reply #12 on: Jul 22, 2008, 07:59:14 PM »

Dude, heather, i love stats and will probably be taking a refresher course this fall myself!  We can be stats buddies!

If we get stuck we'll make ben do our homework.

YES! I like this idea. I really would like to graduate from college before I am 26 so if I can fucking pass two goddamn math classes, it will be a breeze.
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Babar
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Posts: 3305


« Reply #13 on: Jul 22, 2008, 10:45:24 PM »

oh man i can't believe i missed this thread, i wanted to show off!
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Ignatius
Registered user

Posts: 7082


« Reply #14 on: Jul 22, 2008, 11:03:52 PM »

Oh wow my creative writing professor asked me if I could expand this expression: (3a-2b3)-3

Babar, could you help me out?  I think everyone else has gone to sleep...
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bn
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Posts: 2


« Reply #15 on: Jul 22, 2008, 11:28:00 PM »

(1/27)*a^6 *(1/b^9)
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Babar
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Posts: 3305


« Reply #16 on: Jul 22, 2008, 11:30:00 PM »

uh, expand you say...i'm pretty sure i think i know what that means. here's my answer if i understand your inquiry correctly:

a^6 / 27 * b^9

if that answer does not please your heavenly i can contemplate further on the matter at hand if you wish so, sire.

you could expand it further by writing it as:

a^6 * 27^-1 * b^-9

but that would not be considered beautiful in the canon of mathematics.

x post: damn you biggler noefield!
« Last Edit: Jul 22, 2008, 11:42:52 PM by Babar » Logged

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Ignatius
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Posts: 7082


« Reply #17 on: Jul 23, 2008, 01:57:45 AM »

awesome thanks!
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jess
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Posts: 3571


« Reply #18 on: Jul 23, 2008, 09:36:36 AM »

Oh man, I love me some stats, mostly because it lets me do my research, but also in part because it shows how incomplete and thus suspect so much of the information out there is. As my stats prof used to say, it's actually not true that stats can be used to say anything, but you need to understand them first. I think everyone should be required to take the basics of it.

Anyway, if you both do take it, and if you need any more help, I used to tutor for intro. Heather, would you be taking it through the math dept or social sciences? If you can get away with doing it through the psych dept or some such, do, it will probably easier, and you'll have some folks who can't add to save their lives to balance things out.
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elpollodiablo
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Posts: 32624


« Reply #19 on: Jul 23, 2008, 06:25:07 PM »

I can totally appreciate the beauty, symmetry, etc, whatever, of mathematics, but jeezum flubbing crow it must make for the most boring fucking academic existence. No offense intended to anyone, especially bethany's dude, but damn. If I had a choice between ritual suicide and another year of math lectures, I'd be casting about for the sharpest knife available.
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Babar
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Posts: 3305


« Reply #20 on: Jul 23, 2008, 06:47:33 PM »

I can totally appreciate the beauty, symmetry, etc, whatever, of mathematics, but jeezum flubbing crow it must make for the most boring fucking academic existence. No offense intended to anyone, especially bethany's dude, but damn. If I had a choice between ritual suicide and another year of math lectures, I'd be casting about for the sharpest knife available.

i have friends who actively hate maths, but i love maths, although i find it to be to abstract at times, that's why physics are my biggest academic love.
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elpollodiablo
Registered user

Posts: 32624


« Reply #21 on: Jul 23, 2008, 06:58:36 PM »

That post I made was dumb anyway, I'm just frustrated. It is utterly baffling to me how people could devote their lives to this, but then it's utterly baffling to me how someone could devote his life to NASCAR. DIFFRNT STROKES
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Illest Waffle
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Posts: 1240


« Reply #22 on: Jul 23, 2008, 07:16:46 PM »

Look at it this way, algebra is mathematical grammar so you can talk about some beautiful shit later. Calculus is a beautiful elegant thing. Linear Algebra is a wonderful thing too.

All that being said, it isn't for everyone.

Here are useful things:
The only website about math you will ever need
http://mathworld.wolfram.com

If you're bent on learning alone I can't recommend Saxon Publishing's books enough. They use an incremental, building-block approach to lessons, so it is hard to get lost. I've used this book (and their Single Variable Calculus book) to teach home schoolers. It is the proverbial tits.

Why are you learning math? I thought you had a degree in word-smithery.
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elpollodiablo
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Posts: 32624


« Reply #23 on: Jul 23, 2008, 07:21:04 PM »

Ain't quite got a degree yet, brother. This is one of the last requirements for it; I put it off and put it off and put it off and here I am doing a ten week course in five weeks. I ain't bent on learning alone exactly, but what with a full time job, it's hard to ever get any help.

Thanks, though, for the tips! This'll all be over Friday morning, one way or another.
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Andrew_TSKS
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Posts: 39426


« Reply #24 on: Jul 23, 2008, 09:11:04 PM »

oh man, calculus was my waterloo.
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