CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The value of \[\left| \begin{matrix}    {{1}^{2}} & {{2}^{2}} & {{3}^{2}}  \\    {{2}^{2}} & {{3}^{2}} & {{4}^{2}}  \\    {{3}^{2}} & {{4}^{2}} & {{5}^{2}}  \\ \end{matrix} \right|\]is:

    A)  8                            

    B)         \[-8\]

    C)  400                       

    D)         1

    E)  0

    Correct Answer: B

    Solution :

    \[\left| \begin{matrix}    {{1}^{2}} & {{2}^{2}} & {{3}^{2}}  \\    {{2}^{2}} & {{3}^{2}} & {{4}^{2}}  \\    {{3}^{2}} & {{4}^{2}} & {{5}^{2}}  \\ \end{matrix} \right|\] \[=\left| \begin{matrix}    1 & 4 & 9  \\    4 & 9 & 16  \\    9 & 16 & 25  \\ \end{matrix} \right|=\left| \begin{matrix}    1 & 3 & 5  \\    4 & 5 & 7  \\    9 & 7 & 9  \\ \end{matrix} \right|\] \[{{C}_{2}}\to {{C}_{2}}-{{C}_{1}}and\,{{C}_{3}}\to {{C}_{3}}-{{C}_{2}}\] \[=\left| \begin{matrix}    1 & 3 & 2  \\    4 & 5 & 2  \\    9 & 7 & 2  \\ \end{matrix} \right|\]   \[{{C}_{3}}\to {{C}_{3}}-{{C}_{2}}\] \[=\left| \begin{matrix}    1 & 3 & 2  \\    3 & 2 & 0  \\    5 & 2 & 0  \\ \end{matrix} \right|\]   \[\begin{align}   & {{R}_{2}}\to {{R}_{2}}-{{R}_{1}} \\  & {{R}_{3}}\to {{R}_{3}}-{{R}_{2}} \\ \end{align}\] \[=2\left| \begin{matrix}    3 & 2  \\    5 & 2  \\ \end{matrix} \right|=2(6-10)=-8\]


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