If point P lies on the line y = 2, then what is its x-coordinate?
Cannot be determined
Since it is only given that the point P lies on the line y = 2, it can be anywhere on the line y = 2 i.e. -∞< x < +∞ . Therefore the x - coordinate of the point P cannot be determined.
On the other hand, the y – coordinate of the point is 2, because the point lies on line y = 2.
NOTE: If it is given that point P lies on a line x = m then we can directly say that the x – coordinate of the point is ‘m’. Similarly, if point P lies on y = n, then the y coordinate of the point is ‘n’.