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Math Help - factorising

  1. #1
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    factorising

    2x^2+5x+1

    can this be factorised?
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  2. #2
    TD!
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    Sure it is, but since you're asking I'm assuming that you mean over the reals and probably without using radicals. In that case, no.
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  3. #3
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    it must! there's a remainder of 3 from the expression i divided by (x-1)

    but it's not part of the quadratic..
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by x-disturbed-x
    2x^2+5x+1

    can this be factorised?
    Suppose it can be factorised then we would have:

    2x^2+5x+1=2(x-a)(x-b),

    for some a and b. But when x=a, or x=b
    the RHS of the last equation is zero.

    Therefore b and c are the roots of the quadratic
    on the LHS.

    The quadratic formula will give the roots of 2x^2+5x+1,
    which will then allow you to factorise this quadratic.

    RonL
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  5. #5
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    captainblack! you scare me with talk of RHS. there must be an easier way
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  6. #6
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    Actually it's pretty simple simply plug in the values of

    A=2
    B=5
    C=1


    into the quadratic equation
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  7. #7
    TD!
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    A quadratic equation always has 2 roots, if the discriminant is positive, you have two distinct real zeroes, let's call them a and b. You can then always factor (x-a)(x-b). You can find a and b by using the quadratic formula, as CaptainBlack suggested.
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