JEE Main & Advanced Mathematics Three Dimensional Geometry Question Bank Plane

  • question_answer
    If the planes \[x+2y+kz=0\] and \[2x+y-2z=0\] are at right angles, then the value of k is [MP PET 1999]

    A)            \[-\frac{1}{2}\]

    B)            \[\frac{1}{2}\]

    C)            ? 2

    D)            2

    Correct Answer: D

    Solution :

                Obviously, \[\,2\,(1)+1\,(2)-2\,(k)=0\,\,\Rightarrow \,\,k=2\].

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