We can use the points shown on the graph in order to find the rate of change (slope). The points are:
(0,4) and (4,4)
A fast shortcut is just to draw a line from each coordinate to the other. In this case the line would be a horizontal line, which means that the rate of change is zero because the line does not increase or decrease. However we can also prove this.
[tex]\frac{y_2-y_1}{x_2-x_1}
\\ \frac{4-4}{0-4} = \frac{0}{-4} = 0[/tex]
So the rate of change is 0.
