The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have the points (1, 4) and (1, -3). Substitute:
[tex]m=\dfrac{-3-4}{1-1}=\dfrac{-7}{0}\qquad\boxed{!!!!}[/tex]
DIVISION BY ZERO!!!
Answer: The slope is undefined.
It's a vertical line x = 1.
