CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    If\[\Delta =\left| \begin{matrix}    1 & a & {{a}^{2}}  \\    1 & b & {{b}^{2}}  \\    1 & c & {{c}^{2}}  \\ \end{matrix} \right|=k(a-b)(b-c)(c-a),\] then k is equal to:

    A)  \[-2\]                   

    B)                         1                            

    C)         2                                            

    D)         \[abc\]

    E)         \[-1\]

    Correct Answer: B

    Solution :

    \[\Delta =\left| \begin{matrix}    1 & a & {{a}^{2}}  \\    1 & b & {{b}^{2}}  \\    1 & c & {{c}^{2}}  \\ \end{matrix} \right|=\left| \begin{matrix}    1 & a & {{a}^{2}}  \\    0 & b-a & {{b}^{2}}-{{a}^{2}}  \\    0 & c-a & {{c}^{2}}-{{a}^{2}}  \\ \end{matrix} \right|\] \[=(b-a)(c-a)\left| \begin{matrix}    1 & a & {{a}^{2}}  \\    0 & 1 & b+a  \\    0 & c-a & c+a  \\ \end{matrix} \right|\] \[=(b-a)(c-a)(c+a-b-a)\] \[\Rightarrow \]\[(b-a)(c-a)(c-b)\] \[\Rightarrow \]\[k(a-b)(b-c)(c-a)\]         (given)


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