Slope of y axis (vertical line) is “No Slope”

2. When it is lying on top of the y axis, b/c these two lines would be parallel, and the only way two parallel lines intersect is if they are on top of each other(in essence the same line).

3. When, it is lying on top of the x axis. B/C the x axis crosses the y-axis at 0, so a line with slope 0 , in order to cross the yaxis at 0 must be the x axis.

2) When that line is x=0 (and x=0 matches the y-axis at all points, so I guess you can say it intersects infinitely many times at x=0). When x=any other number than 0, the line runs parallel to the y-axis, so it never intersects the y-axis.

3) I’m not sure quite what you mean. Do you mean that the x-coordinate is x=0? When y equals a number (which is the only situation where the slope would be 0), the y-intercept is at (0, the number). For example, for the line y=6, the y-intercept is (0, 6). Remember, intercepts are coordinate pairs.

2. when it IS the y axis

3.when it IS the x-axis

all vertical lines have slopes that are undefined

all horizontal lines have slopes of zero