What is the definition of a graph of a function?

Answer 1

The graph of a function f(x), of an n-dimensional variable x = {x1, x2, ... xn}, is the set of all points in n+1 dimensional space whose coordinates are {x1, x2, ... xn, f(x)}.

In its most simplistic form, if y = f(x), then the graph of the function f(x) is the set of all points, in 2-dimensional space, whose coordinates are (x, f(x)).