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MathGroup Archive 2007

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Re: Is there a way to rewrite Roots[#n] result in easier to read

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80337] Re: Is there a way to rewrite Roots[#n] result in easier to read
  • From: Jepessen <danwolf80_ at _libero_._it>
  • Date: Sat, 18 Aug 2007 05:31:10 -0400 (EDT)
  • References: <fa3dlf$k1$1@smc.vnet.net>

Il Fri, 17 Aug 2007 06:02:23 +0000, Nasser Abbasi ha scritto:

> Hello;
> This is Mathematica 6.01
> 
> Is there a way to make the output of the following DSolve more readable? It 
> contains lots of Root[] with #n in it.
> 
> 
> Remove["Global`*"]
> ode11 = Derivative[1][y][x] -
>      1/Sqrt[Subscript[a, 4]*x^4 + Subscript[a, 3]*x^3 +
>         Subscript[a, 2]*x^2 + Subscript[a, 1]*x + Subscript[a, 0]] ==
>     0;
> DSolve[ode11, y[x], x]
> 
> here is a pic of the output:
> 
> http://12000.org/tmp/081507/output.PNG
> 
> I understand what #'s are for, but was wondering if the output can be 
> written using more 'traditional' form so it will easier to read? i.e having 
> the polynomial whose Roots are being called for, to be explicitly written 
> out or something along those lines?...I tried Simplify[].
> 
> thanks,
> Nasser

Believe me, the generic solution for a 4th equation is mooore long... Roots
is the more efficient way to write a generic solution.

Try

Solve[a*x^4 + b*x^3 + c*x^2 + d*x + e == 0, x]

And see the generic solution in explicit form. You can create particular
cases, replacinx a_x with numbers, and seeing if solution is written in a
more efficient way and, if it's remain with Roots, you can always have
numerical results using N function.

Daniele


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