Thread: How to find if a equation is a function or not?

Can someone explain to what a function is and also answer the title question for me?

Pauls Online Notes : Algebra - The Definition of a Function

The easiest way of all:
Graph the function. Do a "vertical line test."

ie. If at any point you can draw a vertical line through two points, it is NOT a function.

More generally, a function maps a set called the domain to another set called the codomain (or range). The vertical line test only works for functions mapping an input of several variables to the number line, but for functions such as y = x^2, this will do. If the relation fails the vertical line test, it is not a function.