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Math Help - Factorsing help!

  1. #1
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    Factorsing help!

    how do i factorise this ??? Can someone show me how..


    5x^2 -10x = 4x + 3
    So, 5x^2 - 14x - 3 = 0



    Is that right so far, & need to know how to factorise it !

    Thanks in advance..


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  2. #2
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  3. #3
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    5x^2 - 14x - 3 = 0

    (5x + 1)(x - 3) = 0
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  4. #4
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    ^ thanks, can you please explain HOW you did that..
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  5. #5
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    can you please explain HOW you did that..
    lots of practice!

    the factors of the first term 5x^2 are 5x and x, and the factors of the last term -3 are 1 and 3, where each must have opposite signs.

    with that info, start with (5x ... )(x ... ), place 3 and 1 and remember one has to (+) and the other (-) ... just play with the placement so that your middle term comes out to be -14x when you FOIL.
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  6. #6
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    5x^2 - 10x = 4x + 3
    5x^2 - 10x -4x - 3 = 0
    5x^2 - 14x -3 = 0

    In the equation 5x^2-14x-3 the coefficient of x^2 is 5 so the factors must be of the form
    (5x + c)(x + d) = 5x^2 + 5xd + cx + cd = 5x^2 + (5d+c)x +cd
    so 5d + c = -14, cd = -3. The pair of factors of 3 are 1 and 3,
    but for cd = -3 one of c and d must be negative and one positive.
    To satisfy 5d + c = -14, we require c = 1, d = -3

    Therefore 5x^2 - 14 -3 = (5x + 1)(x - 3)
    Therefore the required factorised equation is (5x + 1)(x - 3) = 0
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