Problem 1
Use the slope formula to get
m = (y2 - y1)/(x2 - x1)
m = (-7 - 4)/(-7 - (-7))
m = (-7 - 4)/(-7 + 7)
m = -11/0
The result is undefined as we cannot divide by zero.
This line is vertical and all vertical lines have undefined slopes. This happens when both points have the same x coordinate.
Answer: Undefined
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Problem 2
Use the slope formula again, just with different values of course
m = (y2 - y1)/(x2 - x1)
m = (-9 - (-9))/(2 - (-5))
m = (-9 + 9)/(2 + 5)
m = 0/7
m = 0
In contrast to the previous problem, we can have 0 in the numerator. Dividing 0 over any nonzero value leads to 0.
This line is horizontal as both y coordinates are the same value. All horizontal lines have a slope of 0. You can think of it like
slope = rise/run = 0/1
rise = 0 means we don't move up or down
run = 1 means we move to the right 1 unit
Answer: 0