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Math Help - Finding real numbers of a complex polynomial

  1. #1
    Junior Member Cthul's Avatar
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    Finding real numbers of a complex polynomial

    Find the value of a and b (a,b \in R) given that 2i and 3i are roots of P(z)=z^{3}+aiz^{2}+bz-12i

    I don't understand how to do this.
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  2. #2
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    Hint: If \displaystyle 2i is a root then \displaystyle P(2i) = 0, and if \displaystyle 3i is a root then \displaystyle P(3i) = 0.

    You should end up with two equations in two unknowns ( \displaystyle a,b) that you can solve simultaneously.
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  3. #3
    Junior Member Cthul's Avatar
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    How stupid of me. Thank you.
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