x: 2 | 4 | 6

y: 1 | 0 | -1

Please show me how to find the rule, thanks.
such as...
y= *equation*

as x goes up by 2, y goes down by 1, so

y = -1/2 x + c

Now plug in a point: (2,1)

1 = -1/2 (2) + c
c = 2

so, we have

y = -1/2 x + 2