The numbers 1, 2, 3, … form the set of positive integers
The numbers …, -3, -2, -1 form the set of negative integers
The set of integers consists of the set of positive integers, the set of negative integers and 0
The set of rational numbers consists of the numbers that can be written as a quotient of two integers where and are integers and . We cannot divide by zero. All integers are rational; 2 is because
Rational numbers can be represented by decimal number that terminate (e.g. ), or by nonterminating repeating decimals (e.g. ). Numbers that are represented by nonterminating nonrepeating decimals are called irrational numbers. An irrational numbers cannot be written as an integer divided by an integer (e.g. , ). Together, the rational numbers and the irrational numbers form the set of real numbers.