RAJASTHAN ­ PET Rajasthan PET Solved Paper-2007

  • question_answer
    If \[|{{z}^{2}}-1|=|{{z}^{2}}|+1,\].then z

    A)  lies on real axis

    B)  lies on imaginary axis

    C)  lies on a circle

    D)  lies on an ellipse

    Correct Answer: B

    Solution :

     Given, \[|{{z}^{2}}-1|=|z{{|}^{2}}+1\] \[\Rightarrow \] \[|{{z}^{2}}-1|=|z{{|}^{2}}+|-1|\] From the above it is clear that origin,\[-1\]and \[{{z}^{2}}\]lies on the same line and\[{{z}^{2}}\]and\[-1\] lies on the same side of origin. So,\[{{z}^{2}}\]is a negative number. So, z is purely imaginary. Hence, z lies on y-axis.


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