JEE Main & Advanced Mathematics Three Dimensional Geometry Question Bank Self Evaluation Test - Three Dimensional Geometry

  • question_answer
    The line which passes through the origin and intersect the two lines \[\frac{x-1}{2}=\frac{y+3}{4}=\frac{z-5}{3},\frac{x-4}{2}=\frac{y+3}{3}=\frac{z-14}{4},\] is

    A) \[\frac{x}{1}=\frac{y}{-3}=\frac{z}{5}\]

    B) \[\frac{x}{-1}=\frac{y}{3}=\frac{z}{5}\]

    C) \[\frac{x}{1}=\frac{y}{3}=\frac{z}{-5}\]

    D) \[\frac{x}{1}=\frac{y}{4}=\frac{z}{-5}\]

    Correct Answer: A

    Solution :

    [a] Let the line be \[\frac{x}{a}=\frac{y}{b}=\frac{z}{c}\]            (i) If line (i) intersects with the line \[\frac{x-1}{2}\] \[=\frac{y+3}{4}=\frac{z-5}{3},\] Then \[\left| \begin{matrix}    a & b & c  \\    2 & 4 & 3  \\    4 & -3 & 14  \\ \end{matrix} \right|=0\Rightarrow 9a-7b-10c=0\]  (ii) From (i) and (ii), we have \[\frac{a}{1}=\frac{b}{-3}=\frac{c}{5}\] \[\therefore \] The line is \[\frac{x}{1}=\frac{y}{-3}=\frac{z}{5}\]


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