Algebra-1

The slope of a line is calculated as the change in  divided by the change in , that is .

Case 1: Horizontal line

For a horizontal line, all the -coordinates of the points on the line are the same. So, if we consider two points  and  on a horizontal line, the change in , .

The slope

Case 2: Vertical line

For a vertical line, all the -coordinates of the points on the line are the same. So, if we consider two points  and