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Re: algebraic solutions



Daniel Teitelbaum wrote:
> 
> Hi all,
> 
> I'm a fairly novice Mathematica user, and I'm having a problem.  I asked
> a more experienced user and he could solve it, either.  I hope there is
> a solution and that you all can help.
> 
> I want to find the roots of the following equation:
> 
>     z^5  + 2z^3 - p + 1 = 0
> 
> I want to solve for z in terms of p.  Now, if I pick some random number
> for p, I can get mathematica to solve for z, but I cant get a solution
> in terms of p.  Alternatively, I would like to be able to plot this
> function with p included as part of the vertical axis.
> 
> Thanks in advance for your help,
> 
> Daniel

A quintic equation is hard to solve numerically.  Someone correct me if
I am wrong, but I don't think anyone has cracked the symbolic form of a
quintic solution yet.  Anyway, I do not believe that you would want to
look at the pages and pages of algebra that would result from a
symbolic solution of a quintic.  Remember that, in general, a fifth
order polynomial has five roots.  Do you want to find and plot all of
them?  Are you only interested in a real root?

In any event, I think you are going to have to stick to numeric
solutions unless you want to become a mathematician and crack the
symbolic solution to a quintic yourself.


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