To find the slop:e of two points (x¹, y¹) and (x², y²)
[tex]slope=m=\frac{rise}{run}=\frac{y_2-y_1}{x_2-x_1}[/tex]
In the case of our points (5, -3) and (5, 7)...
[tex]slope=\frac{7-(-3)}{5-5}=\frac{7+3}{0}=\boxed{undefined}[/tex]
Since you cannot divide by zero, the slope of these points (or any vertical line) is considered to be undefined.