JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Expansion of determinants, Solution of equation in the form of determinants and properties of determinants

  • question_answer
    The value of \[\left| \,\begin{matrix}    1 & 1 & 1  \\    bc & ca & ab  \\    b+c & c+a & a+b  \\ \end{matrix}\, \right|\]is [Karnataka CET 2004]

    A) 1

    B) 0

    C) \[(a-b)(b-c)(c-a)\]

    D) \[(a+b)(b+c)(c+a)\]

    Correct Answer: C

    Solution :

     \[\left| \,\begin{matrix}    1 & 1 & 1  \\    bc & ca & ab  \\    b+c & c+a & a+b  \\ \end{matrix}\, \right|\]=\[\left| \,\begin{matrix}    0 & 0 & 1  \\    c(b-a) & a(c-b) & ab  \\    b-a & c+a & a+b  \\ \end{matrix}\, \right|\] \[\{{{C}_{1}}\to {{C}_{1}}-{{C}_{2}},\,{{C}_{2}}\to {{C}_{2}}-{{C}_{3}}\}\] = \[(b-a)\,\,(c-b)\,\,\left| \,\begin{matrix}    0 & 0 & 1  \\    c & a & ab  \\    1 & 1 & a+b  \\ \end{matrix}\, \right|\]= \[(b-a)\,(c-a)\,\,(c-a)\] \[=(a-b)\,\,(b-c)\,\,(c-a)\].


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