JEE Main & Advanced AIEEE Solved Paper-2009

  • question_answer
    If \[\overrightarrow{u},\overrightarrow{v},\overrightarrow{w}\]are non-coplanar vectors and p, q are real numbers, then the equality\[[3\overrightarrow{u},\text{ }p\overrightarrow{v},p\overrightarrow{w}]-[p\overrightarrow{v},\overrightarrow{w},q\overrightarrow{u}]-[2\overrightarrow{w},q\overrightarrow{v},q\overrightarrow{u}]=0\]holds for     AIEEE  Solved  Paper-2009

    A) exactly one value of (p, q)

    B) exactly two values of (p, q)

    C) more than two but not all values of (p, q)

    D) all values of (p, q)

    Correct Answer: A

    Solution :

    \[3{{p}^{2}}[\overrightarrow{u}\overrightarrow{v}\overrightarrow{w}]-pq[\overrightarrow{u}\overrightarrow{v}\overrightarrow{w}]+2{{q}^{2}}[\overrightarrow{u}\overrightarrow{v}\overrightarrow{w}]=0\] \[\Rightarrow \]\[3{{p}^{2}}pq+2{{q}^{2}}=0\] \[p=\frac{q\pm \sqrt{1-24}q}{2\times 3}\] \[p=\frac{q\pm \sqrt{23}iq}{2\times 3}\]\[\Rightarrow \] \[p=0,\text{ }q=0\]


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