so first you have to find the slope, there is an equation for it. it is y2 - y1/ x2 - x1 or just y1 - y2/ x1 - x2 . so input the easiest points. id say f(0) and f(1)
so it will look like
2 - 6/0 - 1
-4/-1
4
so you can now write the equation as
y = 4x + b
now you have to find the y-intercept so input a point. i dont think you should input a point you used to find the slope because you could have made a mistake calculating so lets input f(2)