Q14 of 50 Page 220

Three vertices of a Parallelogram ABCD are A (1, 2, 3), B (– 1, – 2, – 1) and C (2, 3, 2). Find the fourth vertex D.

Given; Three consecutive vertices of a parallelogram ABCD are A (1, 2, 3), B (– 1, – 2, – 1) and C (2, 3, 2)

Let the forth vertex be D(x,y,z).


Midpoint of diagonal AC


Midpoint of diagonal BD



⇒ x=4



⇒ y=7



⇒ z=6


∴ D(4, 7, 6) is the forth vertex.


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