Question 29932
*[tex y2-y1]
-------
*[tex x2-x1]

*[tex y2 = -1] *[tex y1 = 1]
*[tex x2 = 3] *[tex x1 = 3]
{{{m = (-1-1)/(3-3)}}}
{{{m = -2/0}}} ---> m = +∞


slope is undefined.
and since it is on the horinatal axis 
so
*[tex m = 3]


<font color = red>Hence, slope of the line is x=3.</font>
Paul.