### Video Transcript

Which axis is the straight line π₯ equals five parallel to?

Letβs think about the line with the equation π₯ equals five. And now the way of expressing this is the π₯-coordinate is five, which means that every point that lies on this line has an π₯-coordinate which is equal to five. Letβs think about what that would look like. Here we have a set of axes. The point with coordinates five, zero would be on this line. It has an π₯-coordinate of five and a π¦-coordinate of zero. The point with coordinates five, one would also be on this line. This point has an π₯-coordinate of five, and it has a π¦-coordinate of one. In the same way, the point with coordinates five, two also lies on the line.

Below the π₯-axis, the point with coordinates five, negative one will also lie on the line with equation π₯ equals five. And we can continue in this way in both directions. Connecting these points together, we see that the line with equation π₯ equals five is a vertical line passing through every point in the coordinate plane that has an π₯-coordinate of five. As this line is vertical, it is parallel to the π¦-axis.

In general, we can recall that lines with equations of the form π₯ equals π for some constant value of π are vertical lines which are parallel to the π¦-axis. On the other hand, lines with equations of the form π¦ equals π for some constant π are horizontal lines which are parallel to the π₯-axis. Our answer to the question βWhich axis is the straight line π₯ equals five parallel to?β is the π¦-axis.