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What is $max(|z|)$ if $Bigl|frac6z - i2 + 3izBigr|leq1$


Understanding why $int_0^pi/2 sqrt1+cos^2x geq fracpi4bigl( 1 + sqrt2bigr)$Calculate $Bigl|frac1n^zBigr|$.Show that $Pleft(limsuplimits_ttoinftyleft|B_tright|/t>cright)leq Pleft(suplimits_tin[n,n+1]left|B_tright|/n>c;mboxi.o.right)$Why is my solution incorrect? AM GM inequalityComplex numbers $left(frac1+i1-iright)^k = 1$ what is $k$?What are the points of differentiability of $f(z)=vert z vert^2+iota bar z +1$?Verification involving modulus and complex numbersEquality occurring at two different values for a three way inequalityProof for Floor function exponent algebra IdentityReverse Littlewood-Offord problem: lower bound for the number of choices of signs such that $|pm a_1dotspm a_n| leq max|a_i|.$













3












$begingroup$


I'm solving a multiple choice question but my answer is not among the choices and I don't know where I am wrong. The question is this:




What is the $max|z|$ if: $$Bigl|frac6z - i2 + 3izBigr|leq1$$ and $z$ is a complex number.



  1. $frac15$

  2. $frac14$

  3. $frac13$

  4. $frac12$



My solution is this but my answer isn't among them:



$$ biggl|frac6z - i2 + 3izbiggr|leq1Rightarrow |6z-i| leq |2+3iz| Rightarrow |6z-i|^2 leq |2+3iz|^2 $$
$$ Rightarrow (6z-i)overline(6z-i) leq (2+3iz)overline(2+3iz) $$
$$ Rightarrow (6z-i)(6barz+i) leq (2+3iz)(2-3ibarz) $$
$$ Rightarrow 36|z|^2 +6iz - 6ibarz + 1 leq 4 - 6ibarz +6iz + 9|z|^2 $$
$$ Rightarrow 17|z|^2 leq 3 Rightarrow |z|^2 leq frac317 Rightarrow |z| leq sqrtfrac317$$



Where am I wrong? what is the right solution?
Thanks in advance.










share|cite|improve this question











$endgroup$
















    3












    $begingroup$


    I'm solving a multiple choice question but my answer is not among the choices and I don't know where I am wrong. The question is this:




    What is the $max|z|$ if: $$Bigl|frac6z - i2 + 3izBigr|leq1$$ and $z$ is a complex number.



    1. $frac15$

    2. $frac14$

    3. $frac13$

    4. $frac12$



    My solution is this but my answer isn't among them:



    $$ biggl|frac6z - i2 + 3izbiggr|leq1Rightarrow |6z-i| leq |2+3iz| Rightarrow |6z-i|^2 leq |2+3iz|^2 $$
    $$ Rightarrow (6z-i)overline(6z-i) leq (2+3iz)overline(2+3iz) $$
    $$ Rightarrow (6z-i)(6barz+i) leq (2+3iz)(2-3ibarz) $$
    $$ Rightarrow 36|z|^2 +6iz - 6ibarz + 1 leq 4 - 6ibarz +6iz + 9|z|^2 $$
    $$ Rightarrow 17|z|^2 leq 3 Rightarrow |z|^2 leq frac317 Rightarrow |z| leq sqrtfrac317$$



    Where am I wrong? what is the right solution?
    Thanks in advance.










    share|cite|improve this question











    $endgroup$














      3












      3








      3





      $begingroup$


      I'm solving a multiple choice question but my answer is not among the choices and I don't know where I am wrong. The question is this:




      What is the $max|z|$ if: $$Bigl|frac6z - i2 + 3izBigr|leq1$$ and $z$ is a complex number.



      1. $frac15$

      2. $frac14$

      3. $frac13$

      4. $frac12$



      My solution is this but my answer isn't among them:



      $$ biggl|frac6z - i2 + 3izbiggr|leq1Rightarrow |6z-i| leq |2+3iz| Rightarrow |6z-i|^2 leq |2+3iz|^2 $$
      $$ Rightarrow (6z-i)overline(6z-i) leq (2+3iz)overline(2+3iz) $$
      $$ Rightarrow (6z-i)(6barz+i) leq (2+3iz)(2-3ibarz) $$
      $$ Rightarrow 36|z|^2 +6iz - 6ibarz + 1 leq 4 - 6ibarz +6iz + 9|z|^2 $$
      $$ Rightarrow 17|z|^2 leq 3 Rightarrow |z|^2 leq frac317 Rightarrow |z| leq sqrtfrac317$$



      Where am I wrong? what is the right solution?
      Thanks in advance.










      share|cite|improve this question











      $endgroup$




      I'm solving a multiple choice question but my answer is not among the choices and I don't know where I am wrong. The question is this:




      What is the $max|z|$ if: $$Bigl|frac6z - i2 + 3izBigr|leq1$$ and $z$ is a complex number.



      1. $frac15$

      2. $frac14$

      3. $frac13$

      4. $frac12$



      My solution is this but my answer isn't among them:



      $$ biggl|frac6z - i2 + 3izbiggr|leq1Rightarrow |6z-i| leq |2+3iz| Rightarrow |6z-i|^2 leq |2+3iz|^2 $$
      $$ Rightarrow (6z-i)overline(6z-i) leq (2+3iz)overline(2+3iz) $$
      $$ Rightarrow (6z-i)(6barz+i) leq (2+3iz)(2-3ibarz) $$
      $$ Rightarrow 36|z|^2 +6iz - 6ibarz + 1 leq 4 - 6ibarz +6iz + 9|z|^2 $$
      $$ Rightarrow 17|z|^2 leq 3 Rightarrow |z|^2 leq frac317 Rightarrow |z| leq sqrtfrac317$$



      Where am I wrong? what is the right solution?
      Thanks in advance.







      inequality complex-numbers






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      edited Mar 12 at 11:08









      Bernard

      123k741116




      123k741116










      asked Mar 12 at 9:38









      Peyman mohseni kiasariPeyman mohseni kiasari

      12811




      12811




















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          $36-9=27$. You have taken it as $17$. The correct answer is 3).






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            $36-9=27$. You have taken it as $17$. The correct answer is 3).






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              $36-9=27$. You have taken it as $17$. The correct answer is 3).






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                3





                $begingroup$

                $36-9=27$. You have taken it as $17$. The correct answer is 3).






                share|cite|improve this answer









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                $36-9=27$. You have taken it as $17$. The correct answer is 3).







                share|cite|improve this answer












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                answered Mar 12 at 9:42









                Kavi Rama MurthyKavi Rama Murthy

                67.6k53067




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