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Math Help - Factoring equations

  1. #1
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    Factoring equations

    (12-x-x^2)/(x^2-4+3)

    Can someone help me with this?
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  2. #2
    MHF Contributor
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    It's not magic. You have to look at it and encourage it to make sense.

    The numerator is a little funny, so switch it around so that it looks like you expect:

    12-x-x^2 = -x^2 - x + 12 = -(x^2 + x - 12)

    That's better. Now it is easy to see that we need 4*(-3) = 12 and 4 + (-3) = +1

    The denominator should be an eyeball problem.

    (-1)*(-3) = +3 and (-1)+(-3) = -4
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  3. #3
    Member Jonboy's Avatar
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    Once you do what TK said, look for binomials that are (a + b) to cancel.

    like this: \frac{\rlap{---------}(x + 5)(x - 2)}{\rlap{---------}(x + 5)} = x - 2

    but this doesn't cancel: \frac{4 - {\color {red}{\not x}}}{{\color {red} {\not x}}}
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  4. #4
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    Do i keep the negative 1 factored out?

    -1[(x+4)(x-3)
    ____________
    (x-1)(x-3)


    I cancel out the (x-3) right?
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  5. #5
    Senior Member
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    Do i keep the negative 1 factored out?
    It doesn't really matter. However, if you do you need not write the 1 and can just say \frac{-(x+4)}{x-1}

    I cancel out the (x-3) right?
    right
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