Geometry: Slope of a Straight Line

To get the slope of a line, you can use the equation below

A good and perfect explanation of this can be check on this link http://www.purplemath.com/modules/slope.htm


Other's also use this way of method to explain it's coordinates.

where:
A_x  the x coordinate of point A
A_y  the y coordinate of point A
B_x  the x coordinate of point B
B_y  the y coordinate of point B

and for this one, you can check on this link http://www.mathopenref.com/coordslope.html


Additionally, if lines with vertical lines, slope is undefined or doesn't exist. And if lines is going horizontal, then slope will always be 0.

Example:

m = (5) - (-3)/ (4) - (4) = 8/0 which is undefined for points (4, 5) and (4, -3) or UNDEFINED SLOPE

and

m = (4) - (4) / (5) - (-3) = 0/8 = 0 for points/coordinates at (-3, 4) and (5, 4) or ZERO BASED SLOPE