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Math Help - polynomial

  1. #1
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    polynomial

    Hello
    is this right?

    Form a polynomial f(x) with real coheficients having the given degree and zeros.
    zeros: -1,3i. degree 3
    I got x^3+x^2-9x-9.

    thank you so much
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by girl1985 View Post
    Hello
    is this right?

    Form a polynomial f(x) with real coheficients having the given degree and zeros.
    zeros: -1,3i. degree 3
    I got x^3+x^2-9x-9.

    thank you so much
    did you mean to type 3 instead of 3i? if not, you're wrong. the function you gave has the zeros -1, 3, -3
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  3. #3
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    Thank you jhevon.

    So what would be the answer?
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  4. #4
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    Quote Originally Posted by girl1985 View Post
    Hello
    is this right?

    Form a polynomial f(x) with real coheficients having the given degree and zeros.
    zeros: -1,3i. degree 3
    I got x^3+x^2-9x-9.

    thank you so much
    Assuming it is a polynomial in R[x] (over the reals).

    Then if 3i is a solution then so is -3i.

    That means all the polynomials are:
    K(x+1)(x-3i)(x+3i)
    Where K is a non-zero constant polynomial.

    Multiply those factors,
    K(x^3+x^2+9x+9)

    It seems thou are wrong.
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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by girl1985 View Post
    Thank you jhevon.

    So what would be the answer?
    x^3 + x^2 + 9x + 9, you had a -9x and -9, they should have been +, do you see where you made your mistake?
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