If x = 3i is a zero of P(x ) = x4 - 2x3 + x2 - 18x - 72 , then another zero must be x = 2?

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  • Dr D
    Lv 7
    1 decade ago
    Favorite Answer

    x = 3i works.

    x = 2 does not work.

    There will also be zero at x = -3i

    P can be factorized as follows:

    P(x) = (x^2 + 9) * (x^2 - 2x - 8)

    = (x^2 + 9) * (x-4)*(x+2)

    The other roots are x = -2 and +4

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