# User functions

WirisQuizzes Studio uses symbolic notation to work with variables and symbols. This is extremely useful, but `f(x)`

is understood as a multiplication $f\xb7x$. If we want that to be interpreted as a function $f$ evaluated at a point $x$, we need to declare it as a *User function* in *Input options > Input syntax > Define a new function*.

## Example

Let us see a question example.

This is the well-known statement of the Fibonacci sequence. We ask for two answers: the relation and a particular term of the series. Thus, the *Correct answer* editor will look like

Note that since $f$ is marked as a *User function*, it is shown in blue, as any other elemental function ($\mathrm{sin},\mathrm{cos},...$). This feature is also useful when considering the composition of function questions.