Y=-1/2x+1 because b=the y intercept or in other words, the point at which the line crosses the y axis which is at 1. -1/2x because m=the slope and since the line is going down the slope would be negative. Remember rise/run rule, to get to the next point from (0,1) the line goes down 1 and over 2 which would make it 1/2 and since it goes down it is -1/2. The x stays because that is the variable in which you substitute numbers in for to get new points. Thus the y=Mx+b that you are looking for is y=-1/2x+1
