Is the given function linear or nonlinear. If linear determine the slope.

x y = f(x)
1 -2
-2 -14
3 8
4 4
-6 1

If linear, y will change by the same amount if x has fixed increments. In any case, for each interval, the changes will be proportional.

x y dx dy dy/dx
-6 1
-2 -14 4 -15 -15/4
1 -2 3 12 4
3 8 2 10 5
4 4 1 -4 -4

As you can see, it's certainly not linear