Finding the Slope of a Line from a Graph - Concept 68,557 views
If given a line and its graph, we can find the slope easily and quickly. Finding the slope of a line from a graph is one of the simplest ways to calculate slope. One must remember when finding the slope of a line that a downhill line has a negative slope, and an uphill line has a positive slope. Also important in an understanding of the definition of slope and interpreting graphs.
A lot of the time in math you're going to be given a graph of a line or of some other curve but we're just working on lines for now. And you might be asked to find the slope.
There's a couple of different ways to approach it, one way would to find any two points that the line goes through and to count the horizontal change and the vertical change and write them as a fraction. Just make sure sure you write the vertical change on top of the fraction and the horizontal change on the bottom.
Another way you could find the slope from the line in a graph that's given to you is to find any two points that the line goes through and use this equation to calculate the slope. Either one of those methods is totally valid just keep in mind what you're really doing is finding out what number represents how steep the line is.
The last thing to keep in mind is whether the line is a positive or a negative slope. Like for example any line that moves from left to right and increases is a positive slope, and any line that moves from left to right and the line decreases is going to be a negative slope. So make sure you stick on there the appropriate positive or negative sign to match your slope ratio.