JEE Main & Advanced Sample Paper JEE Main Sample Paper-27

  • question_answer
    For all complex numbers z of the form\[1+i\alpha ,\,\alpha \in R\], if \[{{z}^{2}}=x+iy\] then

    A)  \[{{y}^{2}}+4x+2=0\]          

    B)  \[{{y}^{2}}-4x+4=0\]

    C)  \[{{y}^{2}}+4x-4=0\]           

    D)  \[{{y}^{2}}-4x+2=0\]

    Correct Answer: C

    Solution :

    \[z=1+i\alpha ,\,\,\alpha \in R\] Now, \[{{z}^{2}}=x+iy\] \[\Rightarrow \,\,{{(1+i\alpha )}^{2}}+x+iy\] \[\Rightarrow \,\,x=1-{{\alpha }^{2}},\,\,y=2\alpha \] \[\therefore \] On eliminating \[\alpha ,\]we get \[{{y}^{2}}+4x-4=0\]


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