KVPY Sample Paper KVPY Stream-SX Model Paper-6

  • question_answer
    Number of solution of the equation \[{{z}^{3}}+\frac{3{{(\bar{z})}^{2}}}{|z|}=0\] Where z is a complex number is

    A) 2

    B)                    3

    C) 6                                 

    D) 5

    Correct Answer: D

    Solution :

    \[{{z}^{3}}+\frac{3\,{{(\bar{z})}^{2}}}{|z|}=0\]              
    Let \[z=r{{e}^{i\,\theta }}\]
    \[\Rightarrow \] \[{{r}^{3}}{{e}^{i\,3\theta }}+3\,r\,{{e}^{-\,i\,2\,\theta }}=0\]
    Since 'r' cannot be zero
    \[\Rightarrow \]   \[r{{e}^{i\,5\theta }}=-\,3\]       which will hold for
    \[r=3\] and 5 distinct values of \['\theta '\]
    Thus there are five solution.


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