Answer:
k=-5
Step-by-step explanation:
For the points to be collinear any two pair must have the same slope
We find the slope of the 2nd and 3rd points
=1-2/-1--3
=-1/2
Now finding the slope of the 1st and any other point say point 3
1-3/-1-k=-½
-2/-1-k=-½
-4=-1(-1-k)
-4=1+k
k=-4-1
k=-5
PROOF
if the first point is (-5,3)
slope of point 1 and 2
=2-3/-3--5
=-1/2