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Math Help - Algebra - Factoring

  1. #1
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    Algebra - Factoring

    I've tried to factor this for a long time but I can't get it right.

    (x-2y)^3 + 4(2y-x)
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  2. #2
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    Quote Originally Posted by lax600 View Post
    I've tried to factor this for a long time but I can't get it right.

    (x-2y)^3 + 4(2y-x)
    Hello,

    (2y-x)=-(x-2y)




    What have you done ? It's better pointing out mistakes than writing the whole solution ^^
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  3. #3
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    well the directions were for me to factor it completely. Since the problem was (x-2y)^3 + 4(2y - x). I figured I had to use one of those formulas. So at first I multiplied a -1 into (2y - x) to make it the same as the first part. Then it became (x - 2y)^3 + 4(2y - x). So I checked the answer, and it said the answer was:

    (x - 2y)(x - 2y + 2)(x - 2y - 2)

    So then I became confused... Like I don't see there's three -2y's and how the 2 and -2 from 4 went into the parenthesis.... yeah.. hehe
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  4. #4
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    No, when multiplying by -1, it may yield this :

    (x-2y)^3 + 4(2y - x)=(x-2y)^3-4(x-2y)

    =(x-2y)\left((x-2y)^2-\underbrace{4}_{2^2}\right)

    Now, do you know the formula : a^2-b^2=(a-b)(a+b) ?
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  5. #5
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    yeah i know that formula... heh.. forgot that I had to multiply the 4 by -1 too.
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