JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2013

  • question_answer
        If\[a,b\]and c are non-zero real numbers such  that \[\left| \begin{matrix}    bc & ca & ab  \\    ca & ab & bc  \\    ab & bc & ca  \\ \end{matrix} \right|=0,\]then

    A)  only \[\frac{1}{a}+\frac{1}{b\omega }+\frac{1}{c{{\omega }^{2}}}=0\]

    B)  only \[\frac{1}{a}+\frac{1}{b{{\omega }^{2}}}+\frac{1}{c\omega }=0\]

    C)  \[\frac{1}{a\omega }+\frac{1}{b{{\omega }^{2}}}+\frac{1}{c}=0\]

    D)   All of the above

    Correct Answer: D

    Solution :

                     We have, \[\left| \begin{matrix}    bc & ca & ab  \\    ca & ab & bc  \\    ab & bc & ca  \\ \end{matrix} \right|=0\] \[\Rightarrow \]\[{{(ab)}^{3}}+{{(bc)}^{3}}+{{(ca)}^{3}}-3(ab)(bc)(ca)=0\] \[\Rightarrow \]\[(ab+b{{\omega }^{2}}.c+ca\omega )(ab\omega +bc{{\omega }^{2}}+ca)\]                                 \[(ab{{\omega }^{2}}+bc\omega +ca)=0\] \[\Rightarrow \]\[ab+bc{{\omega }^{2}}+ca\omega =0,\]\[ab\omega +bc{{\omega }^{2}}+ca=0,\]                                                 \[ab{{\omega }^{2}}+bc\omega +ca=0\] \[\Rightarrow \]\[\frac{1}{c{{\omega }^{2}}}+\frac{1}{a}+\frac{1}{b\omega }=0,\] \[\frac{1}{c\omega }+\frac{1}{a}+\frac{1}{b{{\omega }^{2}}}=0,\]\[\frac{1}{c}+\frac{1}{a\omega }+\frac{1}{b{{\omega }^{2}}}=0\]              \[\Rightarrow \]\[\frac{1}{a}+\frac{1}{b\omega }+\frac{1}{c{{\omega }^{2}}}=0,\frac{1}{a}+\frac{1}{b{{\omega }^{2}}}+\frac{1}{c\omega }=0,\] \[\frac{1}{a\omega }+\frac{1}{b{{\omega }^{2}}}+\frac{1}{c}=0\]


You need to login to perform this action.
You will be redirected in 3 sec spinner