We have:
* y = 3, Horizontal straight lines have zero slope, since the "rise" is zero.
Answer: 0
* 9x - 3y = 18, We rearrange to the slope form equation, which is: y = mx + b, so:
So the slope is 3.
Answer: 3
* (5,7) and (5, -8) the slope is given by the formula:
So, the "run" is zero, and division by zero is not allowed.
Answer: undefined
* (-4, -1) and (-1, -7)
Answer: - 2