JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Conjugate, Modulus and Argument of complex number

  • question_answer
    If \[{{z}_{1}}=1+2i\] and \[{{z}_{2}}=3+5i\], and then \[\operatorname{Re}\,\left( \frac{{{{\bar{z}}}_{2}}{{z}_{1}}}{{{z}_{2}}} \right)\] is equal to [J & K 2005]

    A) \[\frac{-31}{17}\]

    B) \[\frac{17}{22}\]

    C) \[\frac{-17}{31}\]

    D) \[\frac{22}{17}\]

    Correct Answer: D

    Solution :

    Given\[{{z}_{1}}=1+2i\], \[{{z}_{2}}=3+5i\] and \[{{\bar{z}}_{2}}=3-5i\] \[\frac{{{{\bar{z}}}_{2}}{{z}_{1}}}{{{z}_{2}}}=\frac{(3-5i)\,(1+2i)}{(3+5i)}=\frac{13+i}{3+5i}\] = \[\frac{13+i}{3+5i}\times \frac{3-5i}{3-5i}=\frac{44-62i}{34}\] Then\[\operatorname{Re}\left( \frac{{{{\bar{z}}}_{2}}{{z}_{1}}}{{{z}_{2}}} \right)=\frac{44}{34}=\frac{22}{17}\].


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