Question

Three points, A, B, and C exists in space such that B is "between" A and C. It is known that AB=7, BC=4, and AC=9. Are points A,B, and C collinear? Give a written explanation, supported by mathematical evidence, for your answer.

Answer 1

If the points are collinear, then that would mean that the points lie on the same line when joined to each other. In order to confirm this, the distances between the points must sum up to the length of the line.

AB + BC = AC
7 + 4 ? 9
11 ≠ 9

Since they do not sum up, therefore, the points are not collinear.