J & K CET Engineering J and K - CET Engineering Solved Paper-2008

  • question_answer
    \[\left| \begin{matrix}    1 & x & y+z  \\    1 & y & z+x  \\    1 & z & x+y  \\ \end{matrix} \right|\] is equal to

    A) \[0\]               

    B)  \[x\]

    C)  \[y\]               

    D)  \[xyz\]

    Correct Answer: A

    Solution :

    Let \[\Delta =\left| \begin{matrix}    1 & x & y+z  \\    1 & y & z+x  \\    1 & z & x+y  \\ \end{matrix} \right|\] Applying \[{{C}_{3}}\to {{C}_{3}}+{{C}_{2}}\] \[=\left| \begin{matrix}    1 & x & x+y+z  \\    1 & y & x+y+z  \\    1 & z & x+y+z  \\ \end{matrix} \right|\] \[=(x+y+z)\left| \begin{matrix}    1 & x & 1  \\    1 & y & 1  \\    1 & z & 1  \\ \end{matrix} \right|\] \[=0\] \[(\because \,\,\,{{C}_{1}}\,and\,\,{{C}_{3}}\,are\,identical)\]


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