Question 398174
  <pre><font size = 3 color = "indigo"><b>
Hi
points (-2,1),(a,b) and (4,-1) are collinear
Using the point-slope formula, {{{m =(y[2] - y[1])/(x[2] - x[1])}}}
(-2,1 and 
(4,-1)   m =  2/ -6 = -1/3
(-2,1),
(a,b)  {{{m = (1-b) / (-2-a) = -1/3}}}  |Question states: (a-b) = 1, a = 1+b
(1-b) / (-2-(1+b))     |substituting for a
(1-b)/ (-3 - b) = -1/3 
  -1(-3-b) = 3(1-b)    |cross multiplying
    3 + b = 3 - 3b
        4b = 0
         b = 0  and a = 1    (a = 1+b)
CHECKING our Answer***
(-2,1),
(1,0)  m = 1/-3