CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2010

  • question_answer
    The value of the determinant\[\left| \begin{matrix}    15! & 16! & 17!  \\    16! & 17! & 18!  \\    17! & 18! & 19!  \\ \end{matrix} \right|\]is equal to

    A)  \[15!+16!\]                       

    B)  \[2(15!)(16!)(17!)\]

    C)  \[15!+16!+17!\]              

    D)         \[16!+17!\]

    E)  \[2(15!+16!)\]

    Correct Answer: B

    Solution :

    \[\left| \begin{matrix}    15! & 16! & 17!  \\    16! & 17! & 18!  \\    17! & 18! & 19!  \\ \end{matrix} \right|\] \[=(15!)(16!)(17!)\left| \begin{matrix}    1 & 16 & 17.16  \\    1 & 17 & 18.17  \\    1 & 18 & 19.18  \\ \end{matrix} \right|\] \[=(15!)(16!)(17!)\left| \begin{matrix}    1 & 16 & 272  \\    1 & 17 & 306  \\    1 & 18 & 342  \\ \end{matrix} \right|\] \[=(15!)(16!)(17!)\left| \begin{matrix}    0 & 2 & 70  \\    0 & 1 & 36  \\    1 & 18 & 342  \\ \end{matrix} \right|\] \[=(15!)(16!)(17!)[1-(72-70)]\] \[=2(15!)(16!)(17!)\]


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