Which of following describes a function

A mathematical function is a equation that allows one to input a domain, or a X-value to get and perform a mathematical calculation that gives you outputs.

one examples of this is:

f (x) = -x^3+5

a function can have two domains having the same range but one domain can not have two ranges

Step-by-step explanation:

example:

{ (-2,3), (-3,3), (-4,3) }

Each member of the domain is assigned exactly one member of the range.