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    denamontgomery's Avatar
    denamontgomery Posts: 1, Reputation: 1
    New Member
     
    #1

    Sep 23, 2009, 08:52 AM
    explain factoring to me
    I am trying to factor a quadratic equation
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
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    #2

    Sep 23, 2009, 09:13 AM

    Ok, I'll give and example:

    1. Break down the factors of the term without 'x' and the one with x^2

    -2: 1 x - 2 or 2 x -1
    3: 1x x 3x

    2. Put one set of factors from the first one (-2) with the other set of factors (3) as follows[the factors are put vertically]:

    1ooo1xooio| 1x
    -2ooo3xooo| -6x
    oooooooooo-5x

    Now, multiply the horizontal numbers. 1 x 1x = 1x, -2 x 3x = -6x.
    Then, add both. 1x + (-6x) = -5x

    Now, -5 is not what you're looking for since the term in 'x' in your original equation is +5.

    Try with other factors:

    -1ooo1xooo| -1x
    2ooo3xooio| 6x
    oooooooooo5x

    Now, you have +5x, which is the good one.

    Then, group the diagonal factors in brackets, adding them and putting both groups side by side, don't forget the equal sign and the zero!

    (-1+3x)(2+1x) = 0

    If you expand this, you should have the original equation back.

    Putting the above equation 'cleaner' gives: (3x-1)(x+2)=0

    You know that any number multiplied by zero gives zero? Well, that means that either (3x-1) = 0, or (x+2) = 0.

    3x-1 = 0

    Solve for x to obtain the first answer.

    x+2 = 0

    Solve for x to obtain the second factor.

    The answers for x are 1/3 and -2.

    I hope it helped! :)

    EDIT: Anyway, that's how I learned it the first time.
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #3

    Sep 23, 2009, 09:17 AM

    For a general description of factoring, see:

    Factorization - Wikipedia, the free encyclopedia

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