Section 5.1: Natural Numbers

5.1 Outline

A.  Basic concepts
      1. counting numbers
      2. natural numbers
      3. addition
B. Closure property
      1. definition
      2. closed/not closed
C. Commutative and associative properties
      1. commutative property for addition
      2. associative property for addition
      3. definition of multiplication
      4. closure for multiplication in the set of natural numbers
      5. commutative property for multiplication
      6. associative property for multiplication
D.  Distributive property
E.  Definition of subtraction

5.1 Essential Ideas

Definition of Subtraction
The operation of subtraction is defined in terms of addition:
                         a - b = x means a = b + x