DOCBOOK: Markup for simple mathematical expressions

[Joachim Ziegler <ziegler@mpi-sb.mpg.de>]

How do I correctly markup the expression '(n,k)' in the following phrase:

"The binomial coefficient (n,k) is equal to the number of subsets of 
size k of a set of size n"

Later I want to markup the relationship

(n,k) = (n-1,k-) + (n-1,k)

as being a mahtematical expression/equation.

I've read through the documentation of InlineEquation, but I think 
that's not what I need here. I do not need a nice-looking TeX-picture in 
an InlineMediaObject, I only want to markup some characters as belonging 
to a mathematical expression.

How do I do that?


Greetings,
Joachim