It seems like you started defining a function $f(x)$, but didn't complete it. Could you clarify or complete the definition of the function so I can assist you further? For example, are you working on an equation, a limit, a derivative, or some other concept?

If you'd like, here are some examples to guide you:

1. Is $f(x)$ a polynomial? For example, $f(x) = 3x^2 - 2x + 1$.
2. Are you working on a trigonometric function like $f(x) = \sin(x)$?
3. Are you solving for $f(x)$ in terms of a given condition or equation?
4. Do you need to calculate $f'(x)$ or an integral involving $f(x)$?
5. Is this part of a word problem or specific mathematical topic?

Tip: When defining functions, specifying the type (e.g., polynomial, rational, or trigonometric) helps in solving or analyzing the problem.