[Maxima] my mistake: subst(a,f(x)*g(x),eq)

[Richard Fateman]

ratsubst(a,f(x)*g(x),expression)    may do what you want.

RJF
 

> -----Original Message-----
> From: maxima-bounces at math.utexas.edu 
> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of nijso beishuizen
...snip

> 
> Hi, I'm sorry, It seems that I have simplified my problem too much.
> What if I want to substitute f(x)*g(x) with a?