Answer:
y axis
Explanation:
When you set up an ordered pair, yi always has to be - 1 and x can be anything. To show you what this means, draw an x,y axis.
Plot a few points. Try these (0,-1) (2,-1) and (-2,-1) Now join them. They make a straight perpendicular line.
The line is parallel to the y axis.
A line parallel to the x axis has all the x's the same.
(-1, 1), (-1,2) (-1,4)