If a line graph is parallel to the $y$-axis, then for the line:

If a line graph is parallel to the $y$-axis, then for the line:
  1. $y$ is the same for all points
  2. $x$ is the same for all points
  3. Both $x$ and $y$ change
  4. It must pass through the origin

Solution

A line parallel to the $y$-axis is vertical, of the form $x = c$ (constant), so $x$ is the same for every point on it.

Asked in: IMO

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