Question

For what value of k, will the  point (k,-1), (2,1), (4,5) lie on the line ?

Answer 1

If three points A,B,C are collinear then slope if AB = slope if BC

$\frac{k - 1}{ -1 - 2} = \frac{1 - 5}{2 - 4} \\ k = - 5$