### Functions

Definition

Let A and B be two subsets of ℝ

A relation from A to B is a rule which assigns a member of B to each member of A.

Definition

Let A and B are two subsets of ℝ

A function from A to B is a rule which assigns a unique member of B of each number of A.

Let A and B be two subsets of ℝ

A relation from A to B is a rule which assigns a member of B to each member of A.

Definition

Let A and B are two subsets of ℝ

A function from A to B is a rule which assigns a unique member of B of each number of A.