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Math Help - Quadratics Factoring

  1. #1
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    Quadratics Factoring

    I'm not good at quadratics at all, especially factoring simple problems...

    ex. factor 8k2 - 6k - 5

    My attempt:

    ax2 + bx + c = 0

    ac = -40 b = -6

    find two numbers that the product is -40 and sum is -6

    +4 and -10

    8k2 + 4k - 10k - 5

    group like terms and then factor: This is the step I do not know how to do...

    The answer is (4k - 5)(2k - 1)

    Also, I have know clue where to start on this one:

    0.4m2 + 0.6m -1.8
    Last edited by Mathnood768; April 16th 2013 at 07:53 PM.
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  2. #2
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    Re: Quadratics Factoring

    Hey Mathnood768.

    Hint: Try using the quadratic formula to get f(k) = 0 to solve for k (k1 and k2) and then use the factorization (k - k1)(k - k2) as your factorization and clean it up.

    This is equivalent and it will work for any values of your quadratic.
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  3. #3
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    Re: Quadratics Factoring

    For the second function rewrite the same as equation in simple form. we will get
    4m^2+6m-18=0 OR
    2m^2 + 3m - 9 = 0
    Now proceed as earlier to split the middle term
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  4. #4
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    Re: Quadratics Factoring

    I need to do it the way I wrote down though, I did not learn about quadratic formula. It would be helpful if you could actually use the example I put out.
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  5. #5
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    Re: Quadratics Factoring

    Quote Originally Posted by ibdutt View Post
    For the second function rewrite the same as equation in simple form. we will get
    4m^2+6m-18=0 OR
    2m^2 + 3m - 9 = 0
    Now proceed as earlier to split the middle term
    Now the product ac = -18 and the factors of -18 such that the sum is 3 are 6 and - 3
    So we have
    2m^2 + 6m - 3m - 9 = 0
    (2m-3)(m+3)=0
    That will give m = 3/2 and m = -3
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