Question

Find the value of λ, if the points with position vectors 3 i - 2 j - k, 2 i + 3 j - 4 k, - i + j + 2 k and 4 i + 5 j + λ k are coplanar.

Answer 1

Let the points be A (3, - 2, - 1), B (2, 3, - 4), C (- 1, 1, 2) and D (4, 5, λ)

 = (Position vector of B) - (Position vector of A)