ratsubst(q,x/D^2,a);
factor(%);
ratsubst(x/D^2,q,%);
Does it. Gives
-(x/D-1)*(x/D+1)/(3*x/D+1)^4
> -----Original Message-----
> From: maxima-bounces at math.utexas.edu
> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Daniel Lakeland
> Sent: Friday, June 15, 2007 6:17 PM
> To: maxima at math.utexas.edu
> Subject: Re: [Maxima] grouping the variables in a certain way
>
> On Fri, Jun 15, 2007 at 06:26:29PM -0400, Kamaraju S Kusumanchi wrote:
> >
> > Say I have
> >
> > (%i5) a : D^2 * (D^2 - x^2)/(D+3*x)^4;
> ...
> > How can I change 'a' so that maxima displays
> ....
> > (%i6) b : (1-(x/D)^2)/(1+3*(x/D))^4;
> ...
> >