3.1 Definition of Number line.

A number line is a picture of a straight line on which every point is assumed to correspond to a real number and every real number to a point. It is divided into two symmetric halves by the origin that is the number zero. Positive numbers lie on the right side of zero, and negative numbers lie on the left side of zero.

An arrowhead on either end of the number line suggests that the line continues infinitely in the positive and negative real numbers. We say: "a,b,c,d,….out to infinity".

3.2 Numbers on the number line.

The number line is usually represented as being horizontal. Customarily, positive numbers lie on the right side of zero, and negative numbers lie on the left side of zero. An arrowhead on either end of the drawing is meant to suggest that the line continues indefinitely in the positive and negative real numbers, denoted by R. The real numbers consist of irrational numbers and rational numbers, as well as the integers, whole numbers, and natural numbers (the counting numbers).

                                                                a = b      a equals / is / is equal to b 

                                                                a < b      a is less than b 

                                                                a > b      a is greater than b

a = b    equality

a < b   inequality

a > b   inequality