The vectors \(\hat i+2\hat j+3\hat k\), \(2\hat i+\hat j+\lambda\hat k\) and \(3\hat i+\hat j+2\hat k\) are coplanar if \(\lambda=\)
A. 3
B. \(-\frac95\)
C. \(\frac95\)
D. \(\frac59\)
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Answer: C. \(\frac95\)
\(\begin{vmatrix}1&2&3\\2&1&\lambda\\3&1&2\end{vmatrix}=(2-\lambda)-2(4-3\lambda)+3(2-3)=5\lambda-9=0\).
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· 23 Oct 2026
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