Question

find the value of a if the point ( a, 2) ( 2,4) and (3,4) are collinear

Answer 1

let us assume that it is a triangle and then by using the formula find the area , which is almost equal to 0, then the value of a will come out

Answer 2

We assume that the points are collinear.

If a triangle be formed by these points, the area of the triangle be 0 (zero).

Hence,
a(4-4) - 2(2-3) + 1(8-12) = 0
i.e., 0 + 1 - 4 = 0, which is awkward.

I think that there is a mistake in your problem; the points are not right. Please correct them.