The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have the points (-6, -1) and (-6, 4).
Substitute:
[tex]m=\dfrac{4-(-1)}{-6-(-6)}=\dfrac{4+1}{-6+6}=\dfrac{5}{6}\ !!![/tex]
Dividing by 0 is not possible, therefore the slope is undefined.
It's a vertical line x = -6.
