Real valued function
Usually a function will be given by its relation y = f(x) between the elements x ∈ A and y ∈ B where A is the domain and B is the codomain of f.
For example y = ax + b is a function.
Types of Functions:
Ex: y = x2 + 1; y = log x
Ex: x2 + xy + y2 + 1 = 0; x3 + 7x2y + 2xy2 + y3 – 5x = 0