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Math Help - Factorising a Polynomial

  1. #1
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    Factorising a Polynomial

    Hello there,

    I've been asked to factorise the following expression:
    x^3 - x^2 - 4x + 2

    From what I can tell, using the factor theorem (if f(a) = 0, then (x - a) is a factor of f(x)) and factors of 2 as input to the function, it can't be factorised. Am I right, can it not be factorised? When I'm asked a question like this, should I simply say "cannot be factorised"?

    I'm not asking for answers, because this is for an assignment and I don't want to cheat, I'd just like to know whether I've come to the right conclusion or not.
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  2. #2
    MHF Contributor Siron's Avatar
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    Re: Factorising a Polynomial

    You can't find an a by inspection wherefore f(a)=0, so to solve this equation you need a numerical method. So I would say it can be factorised exactly.
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