JEE Main & Advanced JEE Main Paper (Held on 10-4-2019 Afternoon)

  • question_answer
    Let\[\lambda \] be a real number for which the system of linear equations
    \[x+y+z=6\]
    \[4x+\lambda y\lambda z=\lambda 2\]
    \[3x+2y4z=5\]
    has infinitely many solutions. Then\[\lambda \]is a root of the quadratic equation.
    [JEE Main 10-4-2019 Afternoon]

    A) \[{{\lambda }^{2}}-3\lambda -4=0\]          

    B) \[{{\lambda }^{2}}-\lambda -6=0\]

    C) \[{{\lambda }^{2}}+3\lambda -4=0\]        

    D) \[{{\lambda }^{2}}+\lambda -6=0\]

    Correct Answer: B

    Solution :

    D = 0  \[\left| \begin{matrix}    1 & 1 & 1  \\    4 & \lambda  & -\lambda   \\    3 & 2 & -4  \\ \end{matrix} \right|=0\Rightarrow \lambda =3\]


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