In this lesson, students extend their work with slope triangles to develop a method for finding the slope of any line given the coordinates of two points on the line. Students begin by finding values that make given equations true, specifically reviewing integer operations that involve negative numbers.

Next, students find the slope of a line given a sketch and the coordinates of two points on that line. They generalize how to find slope for any two points and observe that this generalization holds true for both positive and negative slopes (MP8).

Finally, students consider a context that can be represented by a line with a negative slope and they calculate the slope from a graph and interpret the slope in the context.