JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    \[x+ky-z=0\],\[3x-ky-z=0\]and\[x-3y+z=0\] has non-zero solution for \[k\] is equal to:

    A) \[-1\]                                    

    B) \[0\]

    C) \[1\]                                     

    D) \[2\]

    Correct Answer: C

    Solution :

    Key Idea: If the system of equations has non-zero solution, then value of determinant should be zero. Given, system of equations are\[x+ky-z=0\],\[3x-ky-z=0\] and \[x-3y+z=0\] has non-zero solution. \[\therefore \]  \[\left| \begin{matrix}    1 & k & -1  \\    3 & -k & -1  \\    1 & -3 & 1  \\ \end{matrix} \right|=0\] \[\Rightarrow \]               \[1(-k-3)-k(3+1)-1(-9+k)=0\] \[\Rightarrow \]               \[-6k+6=0\] \[\Rightarrow \]               \[k=1\] Note: If the system of equations has zero solution, then the value of determinant should not be zero.


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