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Official Math Homework Help Thread

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DayMan
Posts: 4704 - Karma: 8,748
This might be a repost, but I couldn't find anything similar. Post any problems you are having trouble with here, and if this thread works like it is supposed to, someone else will help you with it. I'll go ahead and start this off:

Create a third degree polynomial that has roots at -2 and 6i and goes through the point (0,4). Write your final answer in standard form.

I honestly don't even know where to start on this one..
Feb 12 2013 9:48PM
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Mr.Sloth
Posts: 5091 - Karma: 13,469
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Feb 12 2013 9:51PM
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DayMan
Posts: 4704 - Karma: 8,748
Yeahh I'm in calc... there's gotta be someone on this website who can help me. This is literally the only thing I'm having trouble in that class with right now, and I have a test tomorrow, so I gotta get this figured out
Feb 12 2013 9:54PM
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babumba
Posts: 28 - Karma: 11
List you out what you know x and y have to equal and guess and check from there? The imaginary answer will be another struggle. I'm in hon. pre calc wbu?
Feb 12 2013 10:04PM
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LoathesRaisins
Posts: 3612 - Karma: 4,735
I made a homework help thread, but its not very useful.

Feb 12 2013 10:05PM
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AwR
Posts: 5147 - Karma: 1,880
pretty sure you would also need -6i as a root as well. As a math teacher I will give you a little help but not the whole answer. The expresseion below should look familiar and a great place to start.
(x+2)(x-6i)(x+6i)


Feb 12 2013 10:09PM
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DayMan
Posts: 4704 - Karma: 8,748
Yeah I figured you could just assume that since it's a complex root it has an opposite conjugate, as does every other complex root. Anyway, so when I get to that, should I try to separate the 6i into root[-6] or i * root[6]? Because I feel like trying to FOIL all that out with those imaginaries in there is going to be messy, and it seems like there should be a cleaner, better way to do it. But hey, what do I know, you're the teacher.
Feb 12 2013 10:20PM
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AwR
Posts: 5147 - Karma: 1,880
actually foiling complex conjugates is one of my favorite lessons to teach!

The thing you have to remember is that i is equal to sqrt(-1) then i^2 is equal to -1.
When we foil (x+6i)(x-6i) we receive
F x^2
O 6ix
I -6ix
L 36i^2

well that simplifies down to

x^2+36i^2

which turns into (using the fact that i^2=-1)

x^2-36

pretty slick right? Then you just multiply it by your other binomial. I am still a little stumped at the whole goes through (0,4) part though right now....
Feb 12 2013 10:28PM
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Piste.Off
Posts: 11586 - Karma: 1,860
I may way off here, its been awhile since I've done any thing like this but:
put your calculator in a+bi mode
graph (x+2)(x-6i)(x+6i)
look at where the line crosses 0,4
Feb 12 2013 10:32PM
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DayMan
Posts: 4704 - Karma: 8,748
Holy shit you just explained that better than my math teacher could in an entire class. This lady has been teaching way too long, and even after countless complaints from students that she sucks at teaching, due to teacher tenure, she can't get fired.
Feb 12 2013 10:33PM
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AwR
Posts: 5147 - Karma: 1,880
Ha ha thanks. Always here to help! Calculus is not my jam, but I teach pre-alg to pre-calc.
Feb 12 2013 10:43PM
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DayMan
Posts: 4704 - Karma: 8,748
Shweet thank you I'll have to keep that in mind next time I need help.. Turns out that is right now haha! Would you happen to know very much about the rational root theorem? I'm sorta struggling with the whole concept of it, and how you use it.
Feb 12 2013 10:50PM
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AwR
Posts: 5147 - Karma: 1,880
^ give me a problem and I may be able to help you out.
Feb 13 2013 6:41PM
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cbj
Posts: 2114 - Karma: 1,136
integral of dx/(x*ln(x))
Feb 13 2013 6:43PM
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Darth.Maul
Posts: 2472 - Karma: 652
Integration by parts is your friend there.
Feb 13 2013 7:29PM
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AwR
Posts: 5147 - Karma: 1,880
do you mean the integral of x*ln(x)?
Feb 13 2013 7:34PM
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cbj
Posts: 2114 - Karma: 1,136
no, I mean the integral of (x*ln(x))^-1 dx
Feb 13 2013 7:35PM
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Black.Bird
Posts: 2566 - Karma: 684
Use substitution.

u= ln(x)
du= (1/x)dx


Integral of (1/u)/du is ln(u)

Answer:
= ln(ln(x)) + C
Feb 13 2013 7:41PM
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AwR
Posts: 5147 - Karma: 1,880
oh word, alright let's see here....

I would first use the rule of negative exponents and rewrite it as

1
x*lnx

and then follow integration by parts or substitution. This is actually a very famous integral problem that is a slick trick. I am off for a run. I will check back to see if you still need assistance.
Feb 13 2013 7:42PM
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bfulmer
Posts: 3053 - Karma: 1,975
www.wolframalpha.com

you are welcome
Feb 13 2013 7:43PM
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Darth.Maul
Posts: 2472 - Karma: 652
This guy's got it!
Feb 13 2013 7:46PM
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cbj
Posts: 2114 - Karma: 1,136
Derp. I kept trying to solve it by parts... Fail. Well this question is in the section of my Calculus textbook that is integration by parts, WTF
Feb 13 2013 7:48PM
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Darth.Maul
Posts: 2472 - Karma: 652
You can use integration by parts but its a little bit harder.
Feb 13 2013 7:53PM
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cbj
Posts: 2114 - Karma: 1,136
Nope prove it!!
Feb 13 2013 8:09PM
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AwR
Posts: 5147 - Karma: 1,880
Well sir, since you are choosing to be an ass. I politely refuse my offer to help you. Have a nice day!
Feb 13 2013 9:06PM
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ALMIGHTYSOSA
Posts: 2800 - Karma: 2,102
I hate foiling problems so much
Feb 13 2013 9:10PM
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ChungBol
Posts: 1075 - Karma: 34
shitty thread
Feb 13 2013 9:50PM
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Darth.Maul
Posts: 2472 - Karma: 652
Fine remind me tomorrow. Im tired and its been a semester since ive done calculus or real math. (stats isnt real math which is what im in now)
Feb 14 2013 1:58AM
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AwR
Posts: 5147 - Karma: 1,880
bhahahahahahahahaha in my 8 years of being on NS this is by far the stupidest thing I have ever read. Stats is used far more often than most math classes by the average joe.
Feb 14 2013 6:26PM
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whoa-dere
Posts: 10596 - Karma: 7,103
what the hell is implicit differentiation?
find y^n by implicit differentiation
x^4+y^4=1

and

x^2-y^2=1


another one
find a quadratic equation function f such that f(3)=33, f'(3)=22, and f''(3)=8.
Feb 14 2013 7:00PM
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whoa-dere
Posts: 10596 - Karma: 7,103
might be hard to see, f(3)'s first derivative=22, f(3)'s second derivative=8
Feb 14 2013 7:01PM
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MilaKunis
Posts: 1480 - Karma: 3,646
For implicit differentation when ever you derive a y value you do what you normally do but then put a Dy/dx in front. For 1 it would be -4x^3/4y^3-= dy/dx
Feb 14 2013 7:14PM
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cbj
Posts: 2114 - Karma: 1,136
No, I was accepting it :) My math textbook was just tricking me, I thought I was supposed to use rules I didn't have to
Feb 15 2013 2:58PM
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EmperorKuzco
Posts: 6660 - Karma: 254
Math is for nerds. I haven't taken a real math class excluding statistics for 2 years
Feb 15 2013 2:59PM
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_Jeffrey_
Posts: 1651 - Karma: 572
gonna bump this because i'm having trouble.

so any ways

how would you go about solving log7(343)^2x=x+5

i know there are different properties/rules/formulas but which one do i use? i'm uber confused
Apr 30 2013 4:26PM
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HentaiHero
Posts: 298 - Karma: 1,099
I feel like this thread would be better as multiple , smaller threads. maybe like trig help, calc help, Algebra 2 help. Just one massive "math" thread would be so hard to get anything done on
Apr 30 2013 4:32PM
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CashmereCat
Posts: 2211 - Karma: 2,394
Re write as 2x times the log base 7 of 343 to start. After that I'm not 100% sure but probably divide by 2x and solve from there?
Apr 30 2013 4:34PM
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Darth.Maul
Posts: 2472 - Karma: 652
Someone's meter is busted! Stats is easy as fuck for me compared to Multi Variable Calc though.
Apr 30 2013 4:39PM
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burntahoegreen
Posts: 191 - Karma: 24
havent done logs in a while but maybe rewrite as: log7(7^3)^2x=x+5
Apr 30 2013 4:43PM
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scrambledeggs
Posts: 380 - Karma: -1,291
english is used far more often than most math classes by the average joe. that doesn't make it "real math" you stupid fuck.
Apr 30 2013 5:24PM
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Chinchi
Posts: 1591 - Karma: 4,211
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Apr 30 2013 6:46PM
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deepfriedtwinkie
Posts: 434 - Karma: 389
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Apr 30 2013 6:49PM
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Chinchi
Posts: 1591 - Karma: 4,211
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Apr 30 2013 6:51PM
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steezburgereddie
Posts: 1059 - Karma: 1,945
I got a real brain teaser.

How reposts about similar things to this one has there been?
Apr 30 2013 7:10PM
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*ninja*
Posts: 2108 - Karma: 1,143
2(x-5)+6x\5= 4x-2

7/8+2a\12=3a\4+ 1/3

HELP PLEASE
May 7 2013 6:55PM
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.AR6rider.
Posts: 15976 - Karma: 8,799
42 to the power of Pi.
May 7 2013 6:55PM
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*ninja*
Posts: 2108 - Karma: 1,143
fuk u some1?
May 7 2013 6:57PM
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Dirac
Posts: 1304 - Karma: 335
http://www.wolframalpha.com/input/?i=2%28x-5%29%2B6x%5C5%3D+4x-2
May 7 2013 7:03PM
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cool_name
Posts: 4295 - Karma: 3,131
im stuck and wolfram says no step by step solution available

(x^53 -1)/(x^7-1)

lim x->1


im stuck i tired do long division but then i get stuck with

(x^46 +x^39+x^32 +x^25 +x^18+x^11 +x^4 ) +(x^4-1)/(x^7-1)

any help?
Sep 18 2013 1:20AM
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DayMan
Posts: 4704 - Karma: 8,748
Bumping this because I'm stuck.

Use implicit differentiation to find dy/dx:

cos (x+y) = x


The fact that it = x is what's throwing me off the most. Anyone want to help me out a bit?
Mar 27 2014 10:44PM
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BBurt
Posts: 1588 - Karma: 3,779
/threads bc Im in honors geometry and I am an algebra man
Mar 27 2014 11:07PM
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