so we have our two points, (-4,-1) and (-8,7) What we need to do to find our slope is y2 - y1 over x2 - x1. Once plugging in the numbers and subtracting it should give you 8/-4. 8 divided by -4 is -2. m = -2. Now to find our "b" we plug in our slope, and plug in one of the two points into the format of y = mx + b.