JEE Main & Advanced Mathematics Determinants & Matrices Question Bank System of linear equations, Some special determinants, differentiation and integration of determinants

  • question_answer
    If \[2x+3y-5z=7,x+y+z=6\], \[3x-4y+2z=1,\] then x = [MP PET 1987]

    A) \[\left| \,\begin{matrix}    2 & -5 & 7  \\    1 & 1 & 6  \\    3 & 2 & 1  \\ \end{matrix}\, \right|\div \left| \,\begin{matrix}    7 & 3 & -5  \\    6 & 1 & 1  \\    1 & -4 & 2  \\ \end{matrix}\, \right|\]

    B) \[\left| \,\begin{matrix}    -7 & 3 & -5  \\    -6 & 1 & 1  \\    -1 & -4 & 2  \\ \end{matrix}\, \right|\div \left| \,\begin{matrix}    2 & 3 & -5  \\    1 & 1 & 1  \\    3 & -4 & 2  \\ \end{matrix}\, \right|\]

    C) \[\left| \,\begin{matrix}    7 & 3 & -5  \\    6 & 1 & 1  \\    1 & -4 & 2  \\ \end{matrix}\, \right|\div \left| \,\begin{matrix}    2 & 3 & -5  \\    1 & 1 & 1  \\    3 & -4 & 2  \\ \end{matrix}\, \right|\]

    D) None of these

    Correct Answer: C

    Solution :

    For the given set of equation, by Cramer?s Rule \[x=\frac{{{D}_{x}}}{D}=\left| \,\begin{matrix}    7 & \,\,3 & -5  \\    6 & \,\,1 & \,\,1  \\    1 & -4 & \,\,2  \\ \end{matrix}\, \right|\,\div \left| \,\begin{matrix}    2 & \,\,3 & -5  \\    1 & \,\,1 & \,\,1  \\    3 & -4 & \,\,2  \\ \end{matrix}\, \right|\].


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