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Math Help - factoring help

  1. #1
    Newbie
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    Dec 2008
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    factoring help

    I need an explanation on how to complete this problem by factoring,
    3x^2+17x+20
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  2. #2
    Super Member Bacterius's Avatar
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    Nov 2009
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    What is the problem ? Anyway, to factorize such equations, you have some methods :
    - identity (before any of the following methods, check if your quadratic is not an identity)
    - guestimate (try a factorization, expand and check)
    - solve & factorize (solve the quadratic by the quadratic formula, and you can easily factorize - yeah I know that perhaps you might be factorizing to solve )
    - brainkiller (the most efficient method once you get the grip, quick and easy (see next post of Mattio))
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  3. #3
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    Joined
    Feb 2010
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    First find the factors of 3x, they are x and 3. Now find the factors of 20, they are 1,2,4,5,10, and 20.

    Notice it is +20, that means your two binomials that you factor it into will either both be addition or subtraction, but that +17 let's you know it's addition.

    Now we have (3x + ?)(x + ?)

    Let's test 4 and 5 as multiples of 20.

    (3x + 5)(x + 4)

    with this you get 3x^2 + 12x + 5x + 20, or 3x^2 + 17x + 20.
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