JEE Main & Advanced Sample Paper JEE Main - Mock Test - 12

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

    A) \[|z+\bar{z}|=\frac{1}{2}\]            

    B) \[z+\bar{z}=1\]

    C) \[|z+\bar{z}|=1\]                 

    D) None of these

    Correct Answer: C

    Solution :

    \[\left| z \right|=\left| z-1 \right|\Rightarrow {{\left| z \right|}^{2}}={{\left| z-1 \right|}^{2}}\]
    \[\Rightarrow \,\,\,z\,\bar{z}=\left( z-1 \right)\,\left( \overline{z}-1 \right)\]
    \[\Rightarrow \,\,\,z\overline{z}=z\overline{z}-z-\overline{z}+1\]
    \[\therefore \,\,\,z+\overline{z}=1\]
    \[\left| z \right|=\left| z+1 \right|\Rightarrow z+\overline{z}=-1\]
    \[\therefore \,\,\left| z+\overline{z} \right|=1\]


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