JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Evening)

  • question_answer
    Let z be a complex number such that \[|z|+z=3+i\](where \[i=\sqrt{-1})\]). Then |z| is equal to [JEE  Main Online Paper (Held on 11-jan-2019 Evening)]

    A) \[\frac{\sqrt{34}}{3}\]                                       

    B) \[\frac{5}{4}\]

    C) \[\frac{\sqrt{41}}{4}\]                           

    D)   \[\frac{5}{3}\]

    Correct Answer: D

    Solution :

    Let \[z=x+iy\] \[\therefore \]\[|z|=\sqrt{{{x}^{2}}+{{y}^{2}}}\] Now\[|z|+z=3+i\] \[\therefore \]\[\sqrt{{{x}^{2}}+{{y}^{2}}}+x+iy=3+i\] \[\Rightarrow \]\[x+\sqrt{{{x}^{2}}+{{y}^{2}}}=3\]and\[y=1\] \[\Rightarrow \]\[x+\sqrt{{{x}^{2}}+}1=3\]and\[\Rightarrow \]\[\sqrt{{{x}^{2}}+}1=3-x\] \[\Rightarrow \]\[{{x}^{2}}+1={{(3-x)}^{2}}\]\[\Rightarrow \]\[x=4/3\] \[\therefore \]\[|z|=\sqrt{\frac{16}{9}+1}=\frac{5}{3}\]


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