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Homework Help: Roots of a complex equation

  1. Mar 20, 2009 #1
    1. The problem statement, all variables and given/known data

    Find all complex solutions to the following equation:

    [tex]3(x^2 + y^2) + (x - iy)^2 + 2(x + iy) = 0 [/tex]

    2. Relevant equations

    I want to use the quadratic formula, but not sure if it applies here.

    3. The attempt at a solution

    This is as far as I can get. What I would like is some idea as to what technique to solve this.
  2. jcsd
  3. Mar 20, 2009 #2
    I could give you two ways of solving this problem. I ask u the following questions first..

    1. What is the solution to x + iy = 0, or say x+1 + i(y-1) = 0??? If you have answered these correctly, then I guess you should go ahead and convert your problem to a

    f(x, y) + i g(x,y) = 0 type, and solve it...

    2. Write z = x + iy. Thats one equation. Conjugate it. Thats another equation. Can u solve them together now??
  4. Mar 21, 2009 #3
    I dont understand this.

    Are you suggesting that the complex conjugates are roots?

    The equation I supplied was expanded where x + iy was originally z and x - iy was "zed bar".

    Does anyone know a procedure to follow to solve this?
  5. Mar 21, 2009 #4
    k, i'll simplify it slightly more for you...

    For method 1.

    I want you to use the formula (a+b)^2 and open up every bracket... then club together all real terms together, and all imaginary terms (with an i) together...

    So, now do u get something like f(x,y) + i g(x,y) = 0 ??? Can you tell me how to solve such a problem??

    If no, then I'll just give one hint.... (x+1) + i ( y-1) = 0 is of the above form with f(x,y) = x+1 and g(x,y) = y-1.

    The only solution to the above is (-1,1). can u tell me why?

    For method 2.

    ok, this i will solve slightly so that i can explain clearly....

    put x + iy = z. then x - iy = z*

    The equation becomes....

    3 z z* + (z*)^2 + 2 z = 0

    Now conjugate the above equation. we get

    3 z* z + z^2 + 2 z* = 0

    You now have two equations with variables z and z*. Solve for them..

    Hint - Subtract them
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