A line "going uphill", moving from left to right, has a positive . Only one of the lines, slopes upwards.
Similarly, a "downhill" line has a negative slope and a horizontal line has a slope, of zero. Therefore,
- Positive slope.
- Negative slope.
What about the vertical line, We can see what result we get when we try to find its slope using the .
We need two points, and on the line.
We can use
The slope formula returned a division by
which is undefined. Therefore, the vertical line has an undefined slope. We can now summarize the slopes for all graphs.
- Positive slope
- Negative slope
- Undefined slope