A function is the relationship between an independent variable (x) and a dependent variable (y). A function can only occur when the independent variable are limited to one use. A function in this case is determined by the { } symbol.
This example is not a function, as the independent variable (2) appears more than once.
The rule is that the independent variable(x) cannot appear more than once as the same value and the dependant variable(y) can appear more than once as the same value.
