Hey there! :D
Plug it into point slope form.
y-y1= m(x-x1)
We need to find m first.
m= y2-y1/x2-x1
3-1/0-1=
2/-1= -2
y-1= -2(x+1)
Distribute.
y-1=-2x-2
Add 1 to both sides.
y=2x-1 <== rule for function
So you can plug any number for x, to find y. Therefore, that is the rule.
I hope this helps!
~kaikers