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Math Help - :(impossible factoring questions

  1. #1
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    Unhappy :(impossible factoring questions

    Hi everyone! I have about 200 problems on factoring, all due tmrw! I'm really stuck on a few of these, and if you could help me that would be great!

    12m^3 y - 75my^3

    10x^3 y + 21x^2 y^2 + 9xy^3

    2a^3 b +11a^2 b^2 - 21ab^3

    6x^3 y + 7x^2 y^2 - 20xy^3

    2x^4 -512

    243 - 3y^4

    625m^4 - 16

    Thanks so much!
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  2. #2
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    Oct 2009
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    Quote Originally Posted by stuckonmath View Post
    Hi everyone! I have about 200 problems on factoring, all due tmrw! I'm really stuck on a few of these, and if you could help me that would be great!

    12m^3 y - 75my^3

    10x^3 y + 21x^2 y^2 + 9xy^3

    2a^3 b +11a^2 b^2 - 21ab^3

    6x^3 y + 7x^2 y^2 - 20xy^3

    2x^4 -512

    243 - 3y^4

    625m^4 - 16

    Thanks so much!

    I'll do one to give you a lead. You do the other ones:

    12m^3 y - 75my^3=3my(4m^2-25y^2)=3my(2m-5y)(2m+5y)

    So first you factor out a common factor ( 3my ) , and then you use the formula for squares difference a^2-b^2=(a-b)(a+b) , with a=2m\,,\,\,b=5y

    Tonio
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