You will need the point slope formula if you don't know it already which is x2-x1 over y2-y1. so in this case, it would be 1-(-1) over -4 -(2) which gives you 1 over 3 simplified and that is your slope. you are then going to substitute one of the point in the slope formula, y=mx+b. so let's say you go with the first point and substitute it, that will give you, 2=1/3(-1)+b and you would solve for b. after you figure out your equation, you multiply 1/3 by -1 to give you -1/3+b=2. Then you would add -1/3 to both sides to get b by itself. You would have b= 2+(-1/3). you with then calculate the difference to get b= 2 1/3 or b= 2.3.