Answer:
0
Explanation:
A vertical (straight up and down) line has an undefined slope
The y values change but the x values do not
m = (y2-y1)/ (x2-x1)
This makes the denominator 0
When we divide by 0, our answer is undefined
When we have a horizontal line, the slope is zero
The x values change but the y values do not
m = (y2-y1)/ (x2-x1)
This makes the numerator 0
The slope will be zero