point slope is y-y1=m(x-x1)
given the point (x1,y1) and the slope m
so
we are given the points we need the slope
slope of the line passing through the oints (x1,y1) and (x2,y2) is
(y2-y1)/(y2-y1)
so, given (2,5) and (-1,8)
slope=(8-5)/(-1-2)=3/-3=-1
so the equation is
y-5=-1(x-2) if we used (2,5) and
y-8=-1(x+1) if we used (-1,8)