It can be positive, negative, zero or nonexistant.
Let's look at all the ways we can calculate slope.
Method 1: Rise Over Run
This is a graphical method. You will need the line graphed, with two points on the line identified.
Start at the leftmost point and count squares to the right until you are directly under the second point. This is the RUN
Now count squares directly up to the second point. This is the RISE
The SLOPE of the line is what you get when you divide the rise by the run.
In the example at the right, the slopeis 8/4 = 2. Notice that it's positive, because the line slants upwards.
Here's an example where the slope is negative.
Notice that the line slants downward. This will result in a negative slope.
Start with the point on the left and rise down a distance of -12 units.
Now run to the right a distance of 4 to get to the second point.
Dividing rise -12 by run 4 gives a slope of -3
Move on to page 2 where we'll look at lines with slope 0 and no slope at all.