The absolute value of a number corresponds to two values, one positive, the other negative. Because the graphs you create using absolute values depict both of these values, they are reflected across the y axis.
Here is an equation involving an absolute value that equates the absolute value of x with y:
y = |x|
For each value on the y axis, you find corresponding negative and positive values of x. Figure 10.10 illustrates a graph of an equation that does not involve an absolute value (y = x). To the right of the graph of this equation, you see the graph of an equation that contains an absolute value. The darkened arrow emphasizes how the negative values of x generate positive y values. From this arises a typical V representation ...