CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The value of\[{{\left( \frac{-1+\sqrt{-3}}{2} \right)}^{26}}+{{\left( \frac{-1-\sqrt{-3}}{2} \right)}^{26}}\]is:

    A)  \[-1\]                   

    B)         1

    C)  0                            

    D)         2

    E)  none of these

    Correct Answer: A

    Solution :

    \[{{\left( \frac{-1+\sqrt{-3}}{2} \right)}^{26}}+{{\left( \frac{-1-\sqrt{-3}}{2} \right)}^{26}}\] \[={{\left( \frac{-1+\sqrt{3}i}{2} \right)}^{26}}+{{\left( \frac{-1-\sqrt{3}i}{2} \right)}^{26}}\] \[={{\omega }^{26}}+{{({{\omega }^{2}})}^{26}}\] \[={{\omega }^{3\times 8+2}}+{{\omega }^{3\times 17+1}}\] \[={{\omega }^{2}}+\omega =-1\]                            \[(\because 1+\omega +{{\omega }^{2}}=0)\]


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