J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    If \[\omega \] is a complex cube root of unity, then \[\frac{a+b\omega +c{{\omega }^{2}}}{a{{\omega }^{2}}+b+c\omega }+\frac{a{{\omega }^{2}}+b\omega +c}{a+b{{\omega }^{2}}+c\omega }\] is equal to

    A)  \[1\]               

    B)  \[2\,\omega \]

    C)  \[2\,{{\omega }^{2}}\]

    D)  \[-1\]

    Correct Answer: D

    Solution :

    \[\frac{a+b\omega +c{{\omega }^{2}}}{a{{\omega }^{2}}+b+c\omega }+\frac{a{{\omega }^{2}}+b\omega +c}{a+b{{\omega }^{2}}+c\omega }\] \[\frac{\omega (a+b\omega +c{{\omega }^{2}})}{(a{{\omega }^{2}}+b\omega +c{{\omega }^{2}})}+\frac{(a{{\omega }^{2}}+b{{\omega }^{2}}+c\omega )}{\omega \,(a+b{{\omega }^{2}}+c\omega )}\] \[=\omega +\frac{1}{\omega }\] \[=\frac{{{\omega }^{2}}+1}{\omega }=-\frac{\omega }{\omega }=-1\] \[(\because \,\,{{\omega }^{2}}+1=-\omega )\]


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