Answer:
A line parallel to the y-axis has no defined slope, and a line parallel to the x-axis has slope of zero.
Step-by-step explanation:
Lines parallel to the y-axis are vertical and are undefined as they don't technically have a gradient.
lines parallel to the x-axis are horizontal and have a gradient of 0 since there is no positive or negative angle, it's just straight.
Hope this helped :)
