       Re: polynomial operations through CoefficientList

• To: mathgroup at smc.vnet.net
• Subject: [mg44758] Re: polynomial operations through CoefficientList
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 25 Nov 2003 00:45:27 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <bps3jo\$9pu\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

CoefficientAdd[lst1_, lst2_] /; Length[lst1] == Length[lst2] := lst1 +
lst2

CoefficientAdd[lst1_, lst2_] /; Length[lst1] > Length[lst2] :=

and

p1[x_] := 1 + k1 x - 2 k2 x^2
p2[x_] := -2 - k3 x

lst1 = CoefficientList[p1[x], x];
lst2 = CoefficientList[p2[x], x];

Regards
Jens

Paolo Bientinesi wrote:
>
> Hello,
> 2 polynomials directly from their CoefficientList's?
>
> example: the polynomials I'm considering are
> p1[x_] := 1 + k1 x - 2 k2 x^2
> p2[x_] := -2 -k3 x
>
> Given
> cf1 = {1,k1,-2 k2}
> and
> cf2 = {-2,-k3}
>
> I would like to get the list
> {-2,-2 k1-k3,4 k2-k1 k3,2 k2 k3}
> for p1[x]*p2[x]
>
> and the list
> {-1,k1-k3,-2 k2}
> for p1[x]+p2[x]
>
> without performing operations like
>
> CoefficientList[
>  cf1.Table[x^i,{i,0,Length[cf1]-1}]*
>  cf2.Table[x^i,{i,0,Length[cf2]-1}], x]
>
> Thanks!
> --
> Paolo
>
> pauldj at cs.utexas.edu                    paolo.bientinesi at iit.cnr.it

```

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