ExamBro
ExamBro
CUET · MATHS · PYQ PAPER 2023

The vectors \(\lambda \hat{i}+\hat{j}+2 \hat{k}, \hat{i}+\lambda \hat{j}-\hat{k}\) and \(2 \hat{i}-\hat{j}+\lambda \hat{k}\) are coplanar if :

  1. A \(\lambda=-2, \lambda=1 \pm \sqrt{3}\)
  2. B \(\lambda=0, \lambda=-1 \pm \sqrt{3}\)
  3. C \(\lambda=1, \lambda= \pm 1+\sqrt{5}\)
  4. D \(\lambda=-1, \lambda=1, \lambda=\sqrt{3}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\lambda=-2, \lambda=1 \pm \sqrt{3}\)

Step-by-step Solution

Detailed explanation

\( \begin{vmatrix} \lambda & 1 & 2 \\ 1 & \lambda & -1 \\ 2 & -1 & \lambda \end{vmatrix} = 0 \) \( \lambda(\lambda^2 - 1) - 1(\lambda + 2) + 2(-1 - 2\lambda) = 0 \) \( \lambda^3 - 6\lambda - 4 = 0 \) \( (\lambda+2)(\lambda^2-2\lambda-2) = 0 \)…
From CUET
Explore more questions on app