-1 because it goes from quadrant 4 to quadrant 2
Look at the picture.
The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have the points (0, 2) and (2, 0). Substitute:
[tex]m=\dfrac{0-2}{2-0}=\dfrac{-2}{2}=-1[/tex]