Ways to Tell if Something Is a Function. Functions are relations that derive one output for each input, or one y-value for any x-value inserted into the equation. For example, the equations y = x + 3 and y = x2 - 1 are functions because every x-value produces a different y-value.
When the function is defined?
In mathematics, an expression is called well-defined or unambiguous if its definition assigns it a unique interpretation or value. For example, if f(x) = 1/x, then f(0) is undefined, but this has nothing to do with the question of whether f(x) = 1/x is well-defined. It is; 0 is simply not in the domain of the function.
What are the rules of a function?
Output variable = Dependent variable = Range. Functions are usually represented by a function rule where you express the dependent variable, y, in terms of the independent variable, x. y = 2.50 ⋅ x. You can represent your function by making it into a graph.