Answer
$m=\text{undefined}$
Work Step by Step
Using $m=\dfrac{y_1-y_2}{x_1-x_2}$ or the Slope Formula, then the slope, $m$, of the line containing the given points, $(
0,0
)\text{ and } (
0,-2
)$, is
\begin{array}{l}
m=\dfrac{0-(-2)}{0-0}
\\\\
m=\dfrac{2}{0}
\\\\
m=\text{undefined}
.\end{array}