


GraphsNumber Lines
We can visualise positive numbers as the distances to points on a line, measured to the right of some chosen "zero point" called the origin.
Negative numbers can then be thought of as
corresponding to distances measured to the left of the origin: We call this a number line. For any number x, the number x (called the negative of x) is the number which is the same distance from the origin as x, but on the opposite side. Note that this is also true when x itself is a negative number, for example (2) = 2.
Since the effect of placing a minus sign before a number is to "reflect" the number about the origin, it follows that for any number x (positive or negative): (x) = x That is, two successive "reflections" take you back to where you started.  Graphs Index  2D coordinates >>
