formatting part of expression



Hi,

I would like to display an equation, both in Maxima and for LaTeX, with
certain parts arranged in a way that's meaningful for the problem.  A
toy example, where I want 1-(a+b) preserved in that form:

--8<---------------cut here---------------start------------->8---
(%i288) eq: c*b/(1-(a+b));
                                      b c
(%o288)                           -----------
                                  - b - a + 1
(%i289) format(eq,%factor/(1-(a+b)));
                                      b c
(%o289)                           -----------
                                  - b - a + 1
--8<---------------cut here---------------end--------------->8---

This does not work.  I would prefer to have something like

--8<---------------cut here---------------start------------->8---
                                     b c
(%o289)                           ---------
                                  1 - b - a 
--8<---------------cut here---------------end--------------->8---

Neither does it work in tex1:

--8<---------------cut here---------------start------------->8---
(%i290) tex1(eq);
(%o290)                      \ifrac{b\,c}{-b-a+1}
(%i291) tex1(format(eq,%factor/(1-(a+b))));
(%o291)                      \ifrac{b\,c}{-b-a+1}
--8<---------------cut here---------------end--------------->8---

Is there a way to do this?  Manually transcribing the equation is a bit
error-prone, especially if it is more complicated.

Best,

Tamas

PS.: This question must have come up before but I guess I am not using
the right search terms because I can't find an answer in the archives.