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)