We can use the slope formula for each of these.
1. 5 - 1 / 4 - 2
4 / 2
2
The slope is 2, and it is rising because it is positive.
2. -5 - 0 / 3 - (-1)
-5 / 4
The slope is -5/4, and it is falling because it is negative.
3. 1 - 1 / -3 - 2
0 / -5
0
The slope is 0, and it is a horizontal line. The value of y is not changing per value of x.
4. -5 - 2 / -1 - (-1)
-7 / 0
Undefined
The slope is undefined because it fails the vertical line test.