Answer:
-7/3
Explanation:
When finding slope from a graph, I always look for places where the graph crosses grid intersections. One of these is the y-intercept, (0, 40).
You have to go quite some distance to find another. It looks to me like the next grid crossing is at (30, -30). At this point, you can do either of two things:
- find the ratio of grid squares
- use the slope formula
What you want to calculate is the ratio of the change in vertical height (rise) to the change in horizontal distance (run). If you use grid squares, you need to make sure the grid has the same number of units horizontally as vertically. (Here a grid square is 10 units in each direction, so we're OK on that point.)
We have observed that the line falls 7 grid squares vertically for a change of 3 grid squares to the right. So, the slope using grid squares is ...
m = rise/run = -7/3
Using the slope formula, we calculate the slope to be ...
m = (y2 -y1)/(x2 -x1)
m = (-30 -40)/(30 -0) = -70/30 = -7/3
The slope of the line is -7/3.