JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Self Evaluation Test - Complex Numbers and Quadratic Equations

  • question_answer
    If \[{{m}_{1}},{{m}_{2}},{{m}_{3}}\] and \[{{m}_{4}}\] respectively denote the moduli of the complex numbers \[1+4i,\,\,3+i,\,\,1-i\] and \[2-3i,\] then the correct one, among the following is

    A) \[{{m}_{1}}<{{m}_{2}}<{{m}_{3}}<{{m}_{4}}\]

    B) \[{{m}_{4}}<{{m}_{3}}<{{m}_{2}}<{{m}_{1}}\]

    C) \[{{m}_{3}}<{{m}_{2}}<{{m}_{4}}<{{m}_{1}}\]

    D) \[{{m}_{3}}<{{m}_{1}}<{{m}_{2}}<{{m}_{4}}\]

    Correct Answer: C

    Solution :

    Let \[{{z}_{1}}=1+4i,\,\,{{z}_{2}}=3+i,\,\,{{z}_{3}}=1-i\,\,and\,{{z}_{4}}=2-3\,i\] \[\therefore \,\,\,{{m}_{1}}=\,\left| {{z}_{1}} \right|,\,\,{{m}_{2}}=\,\left| {{z}_{2}} \right|,\,{{m}_{3}}=\,\,\,\left| {{z}_{3}} \right|\,\,and\,\,{{m}_{4}}=\,\left| {{z}_{4}} \right|\] \[\Rightarrow \,\,\,{{\operatorname{m}}_{1}}=\,\,\sqrt{17},\,\,\,{{m}_{2}}=\,\sqrt{10},\,\,{{m}_{3}}=\sqrt{2},\,\,and\,\,{{m}_{4}}=\sqrt{13},\]            \[\Rightarrow \,\,\,{{\operatorname{m}}_{3}}<{{m}_{2}}<{{m}_{4}}<{{m}_{1}}.\]


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