KVPY Sample Paper KVPY Stream-SX Model Paper-10

  • question_answer
    Given \[A=\left| \begin{matrix}    a & b & 2c  \\    d & e & 2f  \\    \ell  & m & 2n  \\ \end{matrix} \right|\]      \[B=\left| \begin{matrix}    f & 2d & e  \\    2n & 4\ell  & 2m  \\    c & 2a & b  \\ \end{matrix} \right|,\] then

    A) \[2A+B=0\]                  

    B) \[2A-B=0\]

    C) \[A+2B=0\]                  

    D) \[A-2B=0\]

    Correct Answer: B

    Solution :

    \[B=2.2\,\,\left| \begin{matrix}    f & d & e  \\    n & \ell  & m  \\    c & a & b  \\ \end{matrix} \right|\]
     [Taking 2 common from \[{{R}_{2}}\] and \[{{C}_{2}}\]]
    \[=2\,\,\left| \begin{matrix}    2f & d & e  \\    2n & \ell  & m  \\    2c & a & b  \\ \end{matrix} \right|\]      \[=2\,\,\left| \begin{matrix}    2c & a & b  \\    2f & d & e  \\    2n & \ell  & m  \\ \end{matrix} \right|\]
    [\[{{R}_{3}}\leftrightarrow {{R}_{2}},\] then \[{{R}_{2}}\leftrightarrow {{R}_{1}}\]]
    \[=2\,\,\left| \begin{matrix}    a & b & 2c  \\    d & e & 2f  \\    \ell  & m & 2n  \\ \end{matrix} \right|=2A\]
    [\[{{C}_{1}}\leftrightarrow {{C}_{2}}\] and \[{{C}_{2}}\leftrightarrow {{C}_{3}}\]]


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