y=mx+b
m=slope
b=y intercept
alrighty, find the slope
slope between (x1,y1) and (x2,y2) is (y2-y1)/(x2-x1)
the slope between (8,-1) and (-4,2) is (2-(-1))/(-4-8)=(2+1)/(-12)=3/-12=-1/4
y=(-1/4)x+b
find b
subsitute a point
(8,-1)
x=8 and y=-1
-1=(-1/4)(8)+b
-1=-2+b
1=b
the y intercept is y=1 or the point (0,1)