Alasdair McAndrew on Fri, 26 Sep 2014 08:16:29 +0200

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Re: Two questions

Drat - my mail got sent before I was finished)

How can I solve the equations [r4=0,r5=0] for the variables p and q?


On Fri, Sep 26, 2014 at 4:14 PM, Alasdair McAndrew <> wrote:

I've just installed a new version of Pari/GP (2.7.2), compiling from source on a Linux system running Ubuntu 14.04.

My questions are:
  1. When compiling the documentation, the index of users.tex was not compiled in.  I've run "make all", "make doc" (just to make sure) and "make docpdf".  But even through the table of contents claim that the index starts on p325, that page is blank. 
  2. (More generic) - is there any way to solve, over the rationals or over the algebraic numbers, a system of polynomial equations?  I'm applying a Tschirnhaus transformation to a particular set of sixth degree polynomials (which I know to be solvable by an analysis of their Galois groups), but in order to eliminate powers, I need to set several of the coefficients to be zero.

    For example:

    > L1 = 9*t^6 - 35*t^4 + 288*t^3 - 5*t^2 - 1
    > res = polresultant(L1,x-t^2-p*t-q,t)
    > r4 = polcoeff(res,4,x)
    > r5 = polcoeff(res,5,x)