if you are finding a slope you must use the formula y2-y1 / x2-x1
-1-7 -8 -4
------- = ------ = -----
6--4 10 5
now to find the y intercept you need to plug either (-4,7) or (6,-1) into y=mx+b
7 = -4/5(-4) + b
7 = 3.2 + b
3.8 = b
the equation is y = -4/5x + 3.8