Question

What is the slope of the line that passes through (1, 4) and (1, −3)?

Answer 1

The formula of a slope:

$m=\dfrac{y_2-y_1}{x_2-x_1}$

We have the points (1, 4) and (1, -3). Substitute:

$m=\dfrac{-3-4}{1-1}=\dfrac{-7}{0}\qquad\boxed{!!!!}$

DIVISION BY ZERO!!!

Answer: The slope is undefined.

It's a vertical line x = 1.