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Homework Help: Complex equation

  1. Jan 27, 2010 #1
    1. The problem statement, all variables and given/known data
    Draw the set of points in the complex plane satisfying the equation |z + 3i| = 4

    2. Relevant equations

    3. The attempt at a solutionI don't know what z is supposed to be. In class, we've been using z to stand for a complex number (x + yi). Am I supposed to substitute that into the equation? Or, am I supposed to treat z like any real number and find the absolute value?
  2. jcsd
  3. Jan 27, 2010 #2


    Staff: Mentor

    Yes, z is a complex number. The equation you give represents all the complex numbers that are within 4 units of -3i. You could also write the equation as |z - (-3i)| = 4 to emphasize that we're talking about distance. The fact that we're talking about the points that are a fixed distance from a fixed point should suggest a particular kind of shape.
  4. Jan 27, 2010 #3
    Thank you, it's coming back to me now. It the graph of a circle. :*)
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