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Math Help - can some one help me with factoring

  1. #1
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    can some one help me with factoring

    factoring completely

    250x3-128y3

    x2+100
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by dblued View Post
    factoring completely

    250x3-128y3
    250x^3 - 128y^3 = 2(125x^3 - 64y^3) = 2[(5x)^3 - (4y)^3]

    now use the difference of two cubes formula: a^3 - b^3 = (a - b)(a^2 + ab + b^2)

    here of course, your a is 5x and your b is 4y
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  3. #3
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    Quote Originally Posted by dblued View Post
    factoring completely

    250x3-128y3

    x2+100
    250x^3 - 128y^3 = 2(125 x^3 - 64 y^3) = 2([5x]^3 - [4x]^3). Now apply the formula for the difference of two perfect cubes.

    x^2 + 100 = (x + 10i)(x - 10i) where i is the square root of -1.
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  4. #4
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    Quote Originally Posted by Jhevon View Post
    250x^3 - 128y^3 = 2(125x^3 - 64y^3) = 2[(5x)^3 - (4y)^3]

    now use the difference of two cubes formula: a^3 - b^3 = (a - b)(a^2 + ab + b^2)

    here of course, your a is 5x and your b is 4y
    Snap
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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by dblued View Post
    x2+100
    did you mean x^2 ~{\color{red}-}~ 100?

    maybe that's too easy
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  6. #6
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by mr fantastic View Post
    x^2 + 100 = (x + 10i)(x - 10i) where i is the square root of -1.
    i thought about doing that, but complex numbers seemed, well, too advanced here...
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