The following set of four ordered pairs below defines the vertices, in counterclockwise order, of a quadrilateral (four-sided figure)

To find the slope between those vertices, we can write the lines that contains each pair in slope-intercept form. The line equation in slope-intercept form is:
[tex]y=mx+b[/tex]Where m represents the slope and b the y-intercept.
To find those values we just need to substitute our pair of points on this form and create a system for m and b.
For our first pair of points (0, 1) and (-2, 5), we have
[tex]\begin{gathered} b=1 \\ 5=-2m+b \\ \Rightarrow\begin{cases}b=1 \\ m=-2\end{cases} \end{gathered}[/tex]The slope for the first pair is -2.
For the second pair (6, 2) and (4, 6) we have
[tex]\begin{cases}2=6m+b \\ 6=4m+b\end{cases}[/tex]Subtracting the first equation from the first, we get
[tex]\begin{gathered} 2-(6)=6m+b-(4m+b) \\ -4=2m \\ m=-2 \end{gathered}[/tex]The slope for the other side is also -2.