The general equation or standard equation of a straight line is given by

Let be a point not lying on the line (i). Now draw a perpendicular from to the X-axis through the point as shown in the given diagram. It is clear from the diagram that is the abscissa of the point . If is the ordinate of , then are the coordinates of . Since lies on the line (i), so it must satisfy equation of the line, i.e.

Next we consider the difference , i.e.

**(a)**If the point is above the line, then . From equation (iii), we note that only if . But if and or if and .

We conclude that the point is above the line if

(i) and

(ii) and

**(b)** If the point is below the line, then . From equation (iii), we note that only if . But if and or if and .

We conclude that the point is below the line if

(i) and

(ii) and

__NOTE__**:** The point will be on the line if .

** Example:** Determine whether the point lies below or above the line ?

Comparing the given line with general equation of line , here we have , and .

Since is the given point, so .

Now

Since and , so given point line lies above the line.