JEE Main & Advanced Sample Paper JEE Main Sample Paper-45

  • question_answer
    The lines \[\frac{x-3}{1}=\frac{y-}{2}=\frac{z-3}{-\lambda }\] and \[\frac{x-1}{\lambda }=\frac{y-3}{3}=\frac{z-1}{4}\] are coplanar. Then, the number of possible value(s) of \[\lambda \] is

    A)  1                                

    B)  2

    C)  3                                

    D)  0

    Correct Answer: D

    Solution :

     The given lines are coplanar, \[\left| \begin{matrix}    3-1 & 1-3 & 3-1  \\    1 & 2 & -\lambda   \\    \lambda  & 3 & 4  \\ \end{matrix} \right|=0=\left| \begin{matrix}    2 & -2 & 2  \\    1 & 2 & -\lambda   \\    \lambda  & 3 & 4  \\ \end{matrix} \right|\] Applying \[{{C}_{2}}\to {{C}_{2}}+{{C}_{1}},\] \[{{C}_{3}}\to {{C}_{3}}-{{C}_{1}}\] \[\Rightarrow \]            \[\left| \begin{matrix}    2 & 0 & 0  \\    1 & 3 & -\lambda -1  \\    \lambda  & \lambda +3 & 4-\lambda   \\ \end{matrix} \right|\] \[\Rightarrow \]            \[{{\lambda }^{2}}+\lambda +15=0\] Which has normal value of \[\lambda \] \[\therefore \]    \[D=1-4\times 15\] \[=-59<0\]


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