What is the notation for denoting constants in a function?

[Zap]

TL;DR Summary

Looking for the mathematical expression for a parameter in a formula

I remember in grad school encountering the notation for what was referred to as either a parameter of a function or something like a constant variable.

For example, typically we denote a function as f( x ), where x is the independent variable.
If the function f( x ) = ax + b, then a and b are constants.

My question is how would I write the function to denote that it is using constants a and b, which aren't exactly variables but they can be changed.

Something like f( a, b ... x ) ?

I don't remember how to denote it, but I remember there was a way of doing so.
Does anyone know?

 

[fresh_42]

It could be written as $f(x;a,b)$ or $f_{a,b}(x)$ but there is no one and only answer. You can do it as you like as long as it's obvious - or explained - what is meant.

 

[Zap]

Ah, it was the semicolon. That is what I saw. Fantastic!

Thanks for the speedy reply.