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Math Help - Monic Polynomials

  1. #1
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    Monic Polynomials

    Show that there is only one way (disregarding the order of the factors) to factor x^2 +x+3 as a product of monic irreducible polynomials in Z(sub5)[x].

    So, I found that f(1) produces a zero for this polynomial, then I used to the division algorithm to get (x^2 +x+3)/(x-1) = (x+2). However, (x-1)(x+2) does not equal x^2 +x+3, so now I am stuck...
    I also used the quadratic formula to get a pair of complex roots, but I'm unsure as how to prove that is the only way to factor x^2 +x+3 as a product of irreducible monic polynomials in Z(sub5)[z]
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  2. #2
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    Quote Originally Posted by Coda202 View Post
    Show that there is only one way (disregarding the order of the factors) to factor x^2 +x+3 as a product of monic irreducible polynomials in Z(sub5)[x].

    So, I found that f(1) produces a zero for this polynomial, then I used to the division algorithm to get (x^2 +x+3)/(x-1) = (x+2). However, (x-1)(x+2) does not equal x^2 +x+3, so now I am stuck...
    I also used the quadratic formula to get a pair of complex roots, but I'm unsure as how to prove that is the only way to factor x^2 +x+3 as a product of irreducible monic polynomials in Z(sub5)[z]
    <br />
\mathbb{Z}_5 is a field and hence a unique factorization domain [trivially]. also, R[x] is a ufd if R is a ufd, so this is easily seen this way. Also, x^2 +x+3 would only have linear factors, so just test 0, 1, 2, 3, 4.
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  3. #3
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    (x-1)(x+2) DOES equal x^2 +x+3. Remember we a are in a modulo ring.
    x-1 is the same as x+4
    (x+4)(x+2) = x^2 + 6 x + 8 3
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