Re: rational roots

As Andreas said, factor(x^2-1/4) is the way to go. If you want something tidy, here's a quick command:

polrootsQ(p)={

my(f=factor(p),v=matrix(0,2));

for(i=1,#f~,

if(poldegree(f[i,1])==1,

v=concat(v,[-polcoeff(f[i,1],0)/polcoeff(f[i,1],1),f[i,2]])

)

);

};

You can then use

polrootsQ(x^2-1/4)

Charles Greathouse
Analyst/Programmer
Case Western Reserve University

On Tue, Sep 24, 2013 at 1:20 PM, somayeh didari <somayeh_didari@yahoo.com> wrote:

I need to find rational roots of a polynomial in Pari/gp. But when I use polroots command, Pari gives all complex roots. On the other hand rational points are returned in complex type, too. How can i find rational roots in rational type? for example

? polroots(x^2-0.25)
%14 = [-0.5000000000000000000000000000 + 0.E-28*I, 0.500000000000000000000000000
0 + 0.E-28*I]~

But I need [-0.5, 0.5]!!!!!!!!!

somayeh didari