JEE Main & Advanced Sample Paper JEE Main - Mock Test - 1

  • question_answer
    If \[i{{z}^{3}}+{{z}^{2}}-z+i=0\], then |z| is equal to

    A)  0                    

    B) 1

    C) 2               

    D)  None of these

    Correct Answer: B

    Solution :

    [b]: Given, \[i{{z}^{3}}+{{z}^{2}}-z+i=0\] Dividing both side by f and using \[\frac{1}{i}=-i\], we have \[{{z}^{3}}-i{{z}^{2}}+iz+1=0\] \[\Rightarrow \]\[{{z}^{2}}(z-i)+i(z-i)=0\] \[(\because {{i}^{2}}=-1)\] \[\Rightarrow \]\[(z-i)({{z}^{2}}+i)=0\therefore z=i\]or\[{{z}^{2}}=-i\] \[\therefore \]\[|z|=|i|=1\]and\[|{{z}^{2}}|=|z{{|}^{2}}=|-1|=1\therefore |z|=1\]


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