Question

Explain: Graph of y = a is a line parallel to x axis.

Answer 1

y = a where a is any constant number. What does this mean ? This means that if a line is y = a (or let us take a concrete example putting value of a as say, 5) or y = 5, then the y coordinate of every point on the line is 5.

Now, how can you have a line where every point on the line has y coordinate = 5 ? Plot all points on a graph where the y coordinate of all points is 5. You can easily see that when you join all the points, it will be a line parallel to x - axis.

On blue line, all the points have y coordinate as 5, whereas on red line, the value of y coordinate keeps changing for every point. You can see that line y = 5 is parallel to x axis.