Q20 of 50 Page 220

Prove that the points (0, – 1, – 7), (2, 1, – 9) and (6, 5, – 13) are collinear. Find the ratio in which the first point divides the join of the other two.

Given; Three points A (0, – 1, – 7), B (2, 1, – 9) and C (6, 5, – 13)




⇒ AB + BC = AC; ∴ Points A, B and C are collinear.


AB:AC = 2√3:6√3 = 1:3


∴ from the lengths of AB, BC and AC we can say that the first point divides the join of the other two in the ratio 1:3 externally.


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