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Math Help - please help me on this algebreic formular

  1. #1
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    please help me on this algebreic formular

    hiii im 13 and im not very smart i have been given this formular which i dont get this is it:
    The equation 3x2 - 3x = 45 has a solution between 4 and 5.
    i dont think it is possible but plz help as this homework is due tommoro
    thnaks
    love helllp me
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  2. #2
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    Re: please help me on this algebreic formular

    Quote Originally Posted by helppppp View Post
    hiii im 13 and im not very smart i have been given this formular which i dont get this is it:
    The equation 3x2 - 3x = 45 has a solution between 4 and 5.
    i dont think it is possible but plz help as this homework is due tommoro
    I assume that you meant to write 3x^2 - 3x = 45?

    3x^2 - 3x = 45

    \Rightarrow3x^2 - 3x - 45 = 0

    Factor out the greatest common factor, and then factor the remaining trinomial.
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  3. #3
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    Re: please help me on this algebreic formular

    If you want to prove that it has a solution between 4 and 5, move everything to one side:

    3x^2 - 3x - 45 = 0


    If x = 4, 3x^2 - 3x - 45 = -9, and if x = 5, 3x^2 - 3x - 45 = 15. The function is continuous everywhere, so by the intermediate value theorem, there must be a real root between 4 and 5. You can use the quadratic formula to find that root.
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