Re: [Q] Factor
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg1288] Re: [Q] Factor
- From: wagner at bullwinkle.cs.Colorado.EDU (Dave Wagner)
- Date: Wed, 31 May 1995 05:45:48 -0400
- Organization: University of Colorado, Boulder
In article <3qdsb3$454 at news0.cybernetics.net>,
Bernd Last <blast at bendix.swb.de> wrote:
>If I have a funktion like:
>
>f[x_] = (a + b x + c x^2) (2x - 2x^2)
>
>
>How can I factor it like that?
>
>f[x_] = a (2x-2x^2) + b x (2x-2x^2) + c x^2 (2x-2x^2)
> \_______/ \_________/ \___________/
> I II III
>
>And how can I get those factors?
>
>I -> (2x-2x^2)
>II -> x (2x-2x^2)
>III -> x^2 (2x-2x^2)
I suspect the example given is a very simple example of a more general
problem, so I don't know if the following will help or not:
f = (a + b x + c x^2) (2x - 2x^2)
2 2
(2 x - 2 x ) (a + b x + c x )
% /. 2x-2x^2->y
2
(a + b x + c x ) y
Expand[%]
2
a y + b x y + c x y
% /. y->2x-2x^2
2 2 2 2
a (2 x - 2 x ) + b x (2 x - 2 x ) + c x (2 x - 2 x )
Coefficient[%, a]
2
2 x - 2 x
Dave Wagner
Principia Consulting
(303) 786-8371
dbwagner at princon.com
http://www.princon.com/princon