I have following question.

Prove that (1,1) , (-2,-8) and (4,10) lie on straight line.

Now its very easy if we use the slop technique that is we find slop of first two points (1,1) and (-2,-8) which is 3 similarly we find slop of the points (-2,-8) and (4,10) which is also 3. as the slops are equal therefore the points lie on the straight line.

But the problem is here we need to prove it by Distance formula. how can we do this?