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#1 2006-01-28 01:11:22

RauLiTo
Member
Registered: 2006-01-11
Posts: 142

try to get X

hi gus ... how are you big_smile ? i wish u r fine
pic12601uh20vr.gif
try to get X ?


ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...

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#2 2006-01-28 02:05:48

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: try to get X

And that's a quartic equation. They can be solved, but the method is very complex. I think I've probably taken the wrong route. That or the quartic can be factorised into something nicer.


Why did the vector cross the road?
It wanted to be normal.

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#3 2006-01-28 02:24:01

irspow
Member
Registered: 2005-11-24
Posts: 455

Re: try to get X

How precise did you wish to be?  I tried a couple of different ways and none gave me an exact answer.

  Seven iterations of Newton's method, which in this case gave;

  (3x^4+4x^3-x^2+3)/(4x^3+6x^2-2x-6) ≈ 1.6180339887499... and -0.6180339887499

  using 1 and -1 as starting values of x.

  My TI-89 gave (√(5) + 1)/2 and -(√(5) - 1)/2   ( which agrees with above )

  Solving your equation for zero gives;

  x^4 + 2x^3 - x^2 - 6x - 3 = 0

  I don't know the algorithm used by the TI-89 so I had to use Newton's method.  I would think that a quartic formula would be more cumbersome than Newton's method, but I am sure that you can find it on the internet easily.  In short, I don't see an easy way to solve this.

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#4 2006-01-28 04:09:35

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

Re: try to get X

(x²-x-1)(x²+3x+3)


"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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#5 2006-01-29 20:38:49

RauLiTo
Member
Registered: 2006-01-11
Posts: 142

Re: try to get X

when i tried to get X that was my answer also ... so i asked you here guys because u may know ... whatever thank you everybody cool


ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...

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#6 2006-01-30 19:19:22

Tigeree
Member
Registered: 2005-11-19
Posts: 13,847

Re: try to get X

eh, u have a nice signature smile


People don't notice whether it's winter or summer when they're happy.
~ Anton Chekhov
Cheer up, emo kid.

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