JEE Main & Advanced AIEEE Solved Paper-2013

  • question_answer
    If the lines\[\frac{x-2}{1}=\frac{y-3}{1}=\frac{z-4}{-k}\]and\[\frac{x-1}{k}=\frac{y-4}{2}=\frac{z-5}{1}\]are coplanar, then k can have:     AIEEE Solevd Paper-2013

    A) any value                            

    B) exactly one value

    C) exactly two values          

    D) exactly three values

    Correct Answer: C

    Solution :

    Lines are co−planer\[\Rightarrow S.\text{ }D.=0\] \[\Rightarrow \]\[\left| \begin{matrix}    2-1 & 3-4 & 4-5  \\    1 & 1 & -k  \\    k & 2 & 1  \\ \end{matrix} \right|=0\] \[\Rightarrow \]\[\left| \begin{matrix}    1 & -1 & -1  \\    1 & 1 & -k  \\    k & 2 & 1  \\ \end{matrix} \right|=0\] \[(1+2k)+(1+{{k}^{2}})-(2-k)=0\] \[3k+{{k}^{2}}=0\] \[k(k+3)=0\] k = 0 or k = −3 Exactly two values.


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