JEE Main & Advanced Mathematics Vector Algebra Question Bank Application of vectors in three dimensional geometry

  • question_answer
    The equation of the plane containing the line \[\mathbf{r}=\mathbf{i}+\mathbf{j}+\lambda (2\mathbf{i}+\mathbf{j}+4\mathbf{k})\] is

    A)            \[\mathbf{r}.(\mathbf{i}+2\mathbf{j}-\mathbf{k})=3\]

    B)            \[\mathbf{r}.(\mathbf{i}+2\mathbf{j}-\mathbf{k})=6\]

    C)            \[\mathbf{r}.(-\mathbf{i}-2\mathbf{j}+\mathbf{k})=3\]

    D)            None of these

    Correct Answer: A

    Solution :

               The position vector of any point on the given line is \[\mathbf{i}+\mathbf{j}+\lambda (2\mathbf{i}+\mathbf{j}+4\mathbf{k})\]or \[(2\lambda +1)\mathbf{i}+(\lambda +1)\mathbf{j}+4\lambda \mathbf{k}\] which lies on \[\mathbf{r}.(\mathbf{i}+2\mathbf{j}-\mathbf{k})=3\].            Hence, the plane \[\mathbf{r}.(\mathbf{i}+2\mathbf{j}-\mathbf{k})=3\] contains the given line.


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