The slope formula for two points is
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]where these values come from the given points:
[tex]\begin{gathered} (x_1,y_1)=(-13,9) \\ (x_2,y_2)=(20,9) \end{gathered}[/tex]By substituting these values into the slope formula, we have
[tex]\begin{gathered} m=\frac{9-9}{20-(-13)} \\ m=\frac{0}{33} \\ m=0 \end{gathered}[/tex]so, the slope is equal to zero. This imply that the line between these points is horizontal.
