MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Multiplying Polynomials

  • To: mathgroup at smc.vnet.net
  • Subject: [mg117896] Re: Multiplying Polynomials
  • From: Gary Wardall <gwardall at gmail.com>
  • Date: Sat, 2 Apr 2011 17:06:09 -0500 (EST)
  • References: <in6kh7$2iu$1@smc.vnet.net>

On Apr 2, 2:51 am, TBone <TB... at yahoo.com> wrote:
> This is very simple and I freely confess my ingnorance.
>
> I'm trying to set up a generating function to count some letters of the
> alphabet.  Specifically, I need to multiply two polynomials in the
> variable x, do some surgery on the result, and continue with another
> letter.
>
> Here is my problem.
>
> I start with:
>
> expand[(1+ax+a^2x^2+...)*(1+bx+b^2x^2+...)]
>
> and continue with:
>
> expand[(1+ax+bx+abx^2+...)*(1+cx+c^2x^2+...)]
>
> Howerver, it chokes on the following:
>
> expand[(1 + a x + b x + c x + a^2 x^2 + a b x^2 + b^2 x^2 + a c x^2 + b
> c x^2 +
>     c^2 x^2 + a^2 b x^3 + a b^2 x^3 + a^2 c x^3 + a b c x^3 + b^2 c x^3 +
>     a c^2 x^3 + b c^2 x^3 + a^2 b^2 x^4 + a^2 b c x^4 + a b^2 c x^4 +
>     a^2 c^2 x^4 + a b c^2 x^4 + b^2 c^2 x^4 + a^2 b^2 c x^5 + a^2 b c^2 x^5 +
>     a b^2 c^2 x^5 + a^2 b^2 c^2 x^6)*(1 + dx + d^2 x^2)]
>
> What gives?
>
> TIA!!
>
> --TB

Try:

Expand[(1 + a x + b x + c x + a^2 x^2 + a b x^2 + b^2 x^2 + a c x^2 +
    b c x^2 + c^2 x^2 + a^2 b x^3 + a b^2 x^3 + a^2 c x^3 +
    a b c x^3 + b^2 c x^3 + a c^2 x^3 + b c^2 x^3 + a^2 b^2 x^4 +
    a^2 b c x^4 + a b^2 c x^4 + a^2 c^2 x^4 + a b c^2 x^4 +
    b^2 c^2 x^4 + a^2 b^2 c x^5 + a^2 b c^2 x^5 + a b^2 c^2 x^5 +
    a^2 b^2 c^2 x^6)*(1 + dx + d^2 x^2)]

For:
(1 + dx + d^2 x^2)

do you want:?

(1 + d*x + d^2 x^2)


  • Prev by Date: RE: defining a integer greater than one
  • Next by Date: Re: Multiplying Polynomials
  • Previous by thread: Re: Multiplying Polynomials
  • Next by thread: Re: Multiplying Polynomials