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Math Help - Need someone to check this Answer.

  1. #1
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    Answer Check for this problem.



    I know i mess up somewhere on the signs.

    Last edited by Kenlen83; March 22nd 2009 at 04:56 PM.
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  2. #2
    Like a stone-audioslave ADARSH's Avatar
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    Quote Originally Posted by Kenlen83 View Post


    I know i mess up somewhere on the signs.

    x^ 3 +1/8

    = x^3 + (1/2)^3

    = (x+1)(x^2 + 1/4 - x/2 )

    -------------------------------

    Formula used is
    a^3 +b^3

    = (a+b)(a^2 + b^2 - ab)
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  3. #3
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    Quote Originally Posted by Kenlen83 View Post
    I know i mess up somewhere on the signs.
    There's a mnemonic for keeping track of the signs. The factoring formulas are:

    . . . . . \left(a^3\, -\, b^3\right)\, =\, (a\, -\, b)\left(a^2\, +\, ab\, +\, b^2\right)

    . . . . . \left(a^3\, +\, b^3\right)\, =\, (a\, +\, b)(\left(a^2\, -\, ab\, +\, b^2\right)

    You've noticed that the terms inside the formula are always the same; it's only the signs that differ. Use "SOAP" to keep track of the signs:

    Take the sign of the sum or difference of cubes that you're needing to factor. Then look at the two parentheses that you need to fill in:

    . . . . . (a\, \mbox{ S }\, b)\left(a^2\, \mbox{ O }\, ab\, \mbox{ AP }\, b^2\right)

    The letters stand for "the Same sign as what you're factoring", "the Opposite sign from what you're factoring", and "Always use a Plus sign here".

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