A series of points in the form (x, y) is a function if every -value is different.
A graph is a function if a vertical line passes through the graph at most time.
In other words, a relation is a function if for every input pair (x, y) there is only one output y, but a relation is not a function if for some x there is more than one y value.
A function can also be represented algebraically, typically as a formula or equation. The most common way to represent a function is using function notation, such as f(x) = 2x + 3.
Functions play a central role in mathematics and are used to describe many real-world relationships and phenomena. They are widely used in fields such as physics, engineering, economics, and computer science.