CBSE Class 9 Answered

Hi Aditya,

When a line is parallel to X axis, then all points on it are at a constant distance from X axis. 

Distance from X-axis for any point is it's Y - coordinate.

Hence, for all points on such a line, the Y-coordinate is a constant. So we can write the equation as Y = C, where C is a constant.

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Similarly, when a line is parallel to Y axis, then all points on it are at a constant distance from Y axis. 

Distance from Y-axis for any point is it's X - coordinate.

Hence, for all points on such a line, the X-coordinate is a constant. So we can write the equation as X = C, where C is a constant.

Hope this helps.