JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Self Evaluation Test - Determinats

  • question_answer
    What is the value of the determinant \[\left| \begin{matrix}    1 & bc & a(b+c)  \\    1 & ca & b(c+a)  \\    1 & ab & c(a+b)  \\ \end{matrix} \right|?\]

    A) \[0\]

    B) \[abc\]

    C) \[ab+bc+ca\]

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

    Correct Answer: A

    Solution :

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


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