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    Probably will be asking a few questions in this thread throughout the days! :P

    1) Given that 3+i is a root of f(x)=0 where f(x)= 2x^3+ax^2+bx-10

    a) Find the other 2 roots - Which I found to be 3+- 2i. THe answer although shows that the root is 1/2 (0.5) <-- Which is what I dont understand!

    b Find the value of a and b,which I found to be a: -13, b =26 (which are correct)

    Thanks in advance!

    If one answer is complex, a second one must be the conjugate of that surely?

    So the other root is 3 - i.

    This means the third root really is 0.5

    If z is a root, so is z*.

    (x - z)(x - z*)(x - t) = 2x^3 + ax^2 + bx - 10

    You have to find t. Apparently, in your post you said it was 0.5.
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Updated: January 26, 2010

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