A) 6
B) 10
C) 12
D) 24
Correct Answer: C
Solution :
\[\mathbf{a}\,.\,(\mathbf{b}\times \mathbf{c})=\mathbf{a}\,.\,\left| \,\begin{matrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ 1 & 2 & 1 \\ 1 & -1 & 2 \\ \end{matrix}\, \right|=\mathbf{a}\,.\,(5\mathbf{i}-\mathbf{j}-3\mathbf{k})\] \[=(2\mathbf{i}+\mathbf{j}-\mathbf{k})\,.\,(5\mathbf{i}-\mathbf{j}-3\mathbf{k})=10-1+3=12\].You need to login to perform this action.
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