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Thread: quadratic equation

  1. December 15th 2008, 03:54 AM #1
    mathaddict
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    quadratic equation

    Given that a and b are the roots of the quadratic equation 2x^2+5x-4 . Hence , find the values of a^3+b^3

    I know how to find the values of a+b and ab . I am not sure how to expand a^3+b^3 . Thanks for any help
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  2. December 15th 2008, 04:06 AM #2
    mr fantastic
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    Quote Originally Posted by mathaddict View Post
    Given that a and b are the roots of the quadratic equation 2x^2+5x-4 . Hence , find the values of a^3+b^3

    I know how to find the values of a+b and ab . I am not sure how to expand a^3+b^3 . Thanks for any help
    Note that a^3 + b^3 = (a + b)^3 - 3a^2b - 3ab^2 = (a + b)^3 - 3ab(a + b).
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