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Topic: Who knows math?  (Read 2839 times)

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Who knows math?
« on: January 21, 2015, 11:23:33 AM »

    Offline Darkclox

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I know this isn't yahoo answer, but I'm looking for this:

Domain of:

f(x)= 6x^3-2
   2x^3+5x^2+6x     

Who knows math?
« Reply #1 on: January 21, 2015, 11:28:51 AM »

    Offline SantiHN

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All real numbers.

Who knows math?
« Reply #2 on: January 21, 2015, 11:33:25 AM »

    Offline Darkclox

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All real numbers.

It can be all real numbers because this: 0 is a real number and the division by 0 is not defined so it can't be all real numbers. There are some values that make the denominator 0, ofc you can go doing substitutions in the ''x'' but that's not what my professor wants :(

Thanks for the answer btw

Who knows math?
« Reply #3 on: January 21, 2015, 11:34:03 AM »

    Offline Aethelred

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http://www.wolframalpha.com/

My friends use this website when they have doubts.

I believe that it is R\{0}, but honestly speaking, I am not thinking properly today

I tried to: f(x)= (6x^3-2)/(2x^3+5x^2+6x) <=> (6x^3-2)/x(2x^2+5x+6).

Since x(2x^2+5x+6) can't be equal than zero, x != 0 or 2x^2+5x+6 != 0.

But then it went all downhill, since x = [-5 +\- (5^2 -4*2*6)^(1/2)]/2*2 isn't real.

Note: != means different.

I may have done some mistakes.   
« Last Edit: January 21, 2015, 11:41:34 AM by Aethelred »
Am I allowed to be an edgy emo teen girl even though I'm a male adult?

Who knows math?
« Reply #4 on: January 21, 2015, 11:42:55 AM »

    Offline Darkclox

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I factorized, now I'm believing that the domain is all real numbers as Santi stated because when I did it I got complex numbers, my teach said that when you got it like that the domain is all R.

Thanks for both answers and the webpage :D


Actually, the domain is the one that you stated up there R { 0 }. I was looking for both vertical and horizontal asymptote.

Vertical was x=0 and horizontal was y=3

TYYYYYYYYY
« Last Edit: January 21, 2015, 11:46:35 AM by Darkclox »

Who knows math?
« Reply #5 on: January 21, 2015, 11:45:23 AM »

    Offline SantiHN

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It can be all real numbers because this: 0 is a real number and the division by 0 is not defined so it can't be all real numbers. There are some values that make the denominator 0, ofc you can go doing substitutions in the ''x'' but that's not what my professor wants :(

Thanks for the answer btw
X as all real numbers when X =/= 0

Who knows math?
« Reply #6 on: January 21, 2015, 11:48:31 AM »

    Offline West

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If I remember correctly, when you have a polynomial (rough translate from google), the Domain is always all the Real Numbers unless you have a Root (I don't know if you call that on enlgish to the thing V----)

However on your specific example, it's all reals except 0 because it would end up being:
-2
---
0

Nonsense.
« Last Edit: January 21, 2015, 11:50:44 AM by West »
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Who knows math?
« Reply #7 on: January 21, 2015, 11:51:24 AM »

    Offline Darkclox

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If I remember correctly, when you have a polynomial (rough translate from google), the Domain is always all the Real Numbers unless you have a Root (I don't know if you call that on enlgish to the thing V----)

It depends of the function. Rational fuctions need to have a denominator x != 0  ( ! is different )
Functions with root are all the positive values, by that I mean (0,inf)


Thanks all for the answers :)

I was blind tho, I didn't notice that all values in the denominator had an X lol
« Last Edit: January 21, 2015, 11:53:39 AM by Darkclox »

Who knows math?
« Reply #8 on: January 21, 2015, 11:54:08 AM »

    Offline West

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Yup, in case you are new to this topic, to get the domain is basically numbers that you replace on the X and end up giving you (after doing all the math) an answer with sense, unlike something... 1/0.

So unless you have any weird thing like Roots, or other stuff like in this case a "/", a rough polynomial will always have as domain all real numbers.
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Who knows math?
« Reply #9 on: January 21, 2015, 12:14:57 PM »

    Offline Aethelred

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I was blind tho, I didn't notice that all values in the denominator had an X lol
I have to tell you a secret. I was terrible at maths. But I enjoyed maths, always did. The fact that I liked it made me one of the best students in maths on my class. I got into college and I am currently studying Computer and telematics engineering (I believe that's how it is called in english). In one of my Calculus classes, I met something called primitives. I am terrible at maths once again.
My point is: Don't give up (Even though that you'll probablly forget a lot of this when you are like 80 years old)
« Last Edit: January 21, 2015, 12:17:02 PM by Aethelred »
Am I allowed to be an edgy emo teen girl even though I'm a male adult?

Who knows math?
« Reply #10 on: January 21, 2015, 12:20:57 PM »

    Offline Darkclox

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Math is hard to forget once learned, well that's my case.

Who knows math?
« Reply #11 on: January 21, 2015, 12:32:01 PM »

    Offline Aethelred

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I can't memorize a lot of things. This has been my weakness. I know that if I put effort into it, I might get better with time, though I lack motivation to do so.
Am I allowed to be an edgy emo teen girl even though I'm a male adult?

Who knows math?
« Reply #12 on: January 21, 2015, 12:38:07 PM »

    Offline Rogue

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If this was science i woukd have u but i hated math so sry man
    
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Join Radiant Dawn

Who knows math?
« Reply #13 on: January 21, 2015, 01:38:25 PM »

    Offline SantiHN

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If this was science i woukd have u but i hated math so sry man
I feel ya. I always watched documentaries and stuff on Discovery, History, NatGeo, kept searching stuff, reading articles and absolutely loved physics, BUT NOT math. Math always stressed me out lots.
Funny, 'cause now i'm studying engineering.

Who knows math?
« Reply #14 on: January 21, 2015, 01:40:17 PM »

    Offline Darkclox

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Physics = maths in action.

Who knows math?
« Reply #15 on: January 21, 2015, 01:47:40 PM »

    Offline SantiHN

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Physics = maths in action.
Indeed. Of course now I know physics as a mathematical form. It's a thing I need for my career, but when I was younger I could perfectly explain momentum, gravity, inertia, why light doesn't escape black holes, how light can get bent. Basically facts. Physics in a verbal form, without diving into the actual research and data of it.

Who knows math?
« Reply #16 on: January 21, 2015, 01:54:05 PM »

    Offline Vroku

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9+10=21

Who knows math?
« Reply #17 on: January 21, 2015, 02:07:57 PM »

    Offline Aeoru

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c=8 is the solution to this problem

Who knows math?
« Reply #18 on: January 21, 2015, 02:45:43 PM »

    Offline Shiro

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9+10=21

Holy crap! That dude knows what he's talking about.
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Who knows math?
« Reply #19 on: January 21, 2015, 03:06:14 PM »

    Offline Nady93

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(6x^3-2)/(2x^3+5x^2+6x)

(=/= -> Not equal )

Just Denominator =/= 0,
(2x^3+5x^2+6x) =/= 0

So we have to solve: (2x^3+5x^2+6x) = 0
Take off x before the bracket: x(2x^2+5x+6)=0
x=/=0 and (2x^2+5x+6) =/= 0
Δ=b^2 - 4ac
Δ=5*5-4*2*6
Δ=25-48=-23 so we have NOT real solutions

Domain = R-{0}

Who knows math?
« Reply #20 on: January 21, 2015, 10:16:20 PM »

    Offline Raziel

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I know math :)) its actualy very easy im gonna solve it for you and explain it
Spoiler for Hidden:
Sorry for my hand writing , its horrible....
 Nady23 and Aethelred :D gave you the answer earlier :D
« Last Edit: January 21, 2015, 11:20:50 PM by Raziel »

Who knows math?
« Reply #21 on: January 22, 2015, 12:24:56 AM »

    Offline Darkclox

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I know math :)) its actualy very easy im gonna solve it for you and explain it
Spoiler for Hidden:
Sorry for my hand writing , its horrible....
 Nady23 and Aethelred :D gave you the answer earlier :D

I did it that way, then the vertical asymptote is x=0 'cause x=0 isn't in the domain. The other one is dividing both numerator and denominator leading coefficient grades, that gave me y=3.

Thanks all.

Who knows math?
« Reply #22 on: January 22, 2015, 02:21:57 AM »

    Offline Tomlanji

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