Observing the given graph, we can see that the line is decreasing over its entire interval.
Thus, the graph has a negative slope. Next we need to find two points on the graph.
When we look at the graph, we can see that the line is everywhere at the same distance from the -axis.
Since the graph is parallel to the -axis we say that it is a horizontal line. Next we wish to find the slope of the graph. Once it has been established that a line is horizontal it is not necessary to calculate its slope. That is because all horizontal lines have the same slope, Here we will show how it can be proved that the slope really is We will then use the slope formula. Let's find two points on the graph, and that we can use in the slope formula.
In this graph we can see that the line is increasing over its entire interval.
A line which is increasing has a positive slope. Next, we want to find the slope of the line. For this we will use the slope formula. We need to find two points on the graph as these are needed in the slope formula.