Introduction to slope of a line, and how to read the slope from a graph
The SLOPE of a line is basically its steepness. We measure it as the ratio of the change in the y-values to the change in the x-values. As such, we can determine the slope from a table of x and y-values. Using a graph, we find two points on the graph and draw a right triangle. Then we check the increase (or decrease) in y-values and the increase in x-values, and write a ratio of the two.
Slope can be negative - in that case the line is descending (going as if "downhill").
Most of the lines in this lesson go through the origin and are of the form y = mx, where m is the slope. Lastly we also look at some lines that don't go through origin and whose equations are of the form y = mx + b, where b is a constant signifying where the line crosses the y-axis (aka y-intercept).
See also
Writing equations for word problems — video lesson
Math Mammoth Grade 7 curriculum (pre-algebra)