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Re: Multiplying Polynomials

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  Re: Multiplying Polynomials Bob Hanlon <hanlonr@cox.net> - 2011-04-02 22:05 +0000

#1443 — Re: Multiplying Polynomials

Use Expand vice expand


Bob Hanlon

---- TBone <TBone@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

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