To find the slope you have to use this formula:
[tex]\frac{y2-y1}{x2-x1}[/tex]
First chose any 2 random points from the graph, im gonna chose (0,1) and (-4,4). It doesn't matter which one is the x1 or x2, what matter is they have to be in the same order, you can't have (-4,4) as a (x1,y2), That's wrong.
[tex]\frac{(1)-(4)}{4-0}[/tex]
= -3/4
