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Math Help - I need help with a 2nd grade equations

  1. #1
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    I need help with a 2nd grade equations

    Hi!
    Could someone please solve this equation for me and try to explain how you did that. 4*(x-1)^2+1/3=7/9

    I do know the answer for this equation. But I don't know how to think when solving it and how to get the answer.
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  2. #2
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    Re: I need help with a 2nd grade equations

    Quote Originally Posted by jimutt View Post
    Hi!
    Could someone please solve this equation for me and try to explain how you did that. 4*(x-1)^2+1/3=7/9

    I do know the answer for this equation. But I don't know how to think when solving it and how to get the answer.
    4(x-1)^2 + \frac{1}{3} = \frac{7}{9}

    multiply every term by 9 to clear the fractions ...

    36(x-1)^2 + 3 = 7

    subtract 3 from both sides ...

    36(x-1)^2 = 4

    divide both sides by 36 and reduce ...

    (x-1)^2 = \frac{1}{9}

    "un"square both sides ...

    x-1 = \pm \frac{1}{3}

    add 1 to both sides ...

    x = 1 \pm \frac{1}{3}

    so, the two solutions are x = \frac{4}{3} and x = \frac{2}{3}
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  3. #3
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    Re: I need help with a 2nd grade equations

    This is a second grade problem? Seven year olds are expected to be able to do this?
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    Re: I need help with a 2nd grade equations

    Thank you very much skeeter!
    Never realised that it was so easy.

    HallsofIvy: Well, not really :P I just translated the name we use for this kind of equations here in Sweden directly to english. So It maybe isn't very correct
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  5. #5
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    Wink Re: I need help with a 2nd grade equations

    Quote Originally Posted by HallsofIvy View Post
    This is a second grade problem? Seven year olds are expected to be able to do this?
    check this out ...

    http://http://www.wired.com/magazine/2011/07/ff_khan/all/1

    ... won't be long until we're all out of a job.
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  6. #6
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    Re: I need help with a 2nd grade equations

    Okey, here you've got one more equation to help me out with. I have to say that this book really sucks at explaining (and so does my math teacher also, sadly enough).

    2x^2+4x+40=3x^2-2x


    And by the way. It would be extreamly nice if you could help me out two factorizing problems also:

    1. 2x+2a2b(x+a)

    2. a^(x+2)-a^(2x)
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  7. #7
    MHF Contributor Siron's Avatar
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    Re: I need help with a 2nd grade equations

    Put all the terms to one side, so you get:
    2x^2+4x+40-3x^2+2x=0
    \Leftrightarrow -x^2+6x+40=0
    Use the quadratic formula to continue.

    Ex 2:
    Determine which factor the terms have in common, for example:
    2. a^{x+2}-a^{2x}=a^{x}\cdot a^{2} - (a^{x})^2=...
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  8. #8
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    Re: I need help with a 2nd grade equations

    Quote Originally Posted by jimutt View Post
    Okey, here you've got one more equation to help me out with. I have to say that this book really sucks at explaining (and so does my math teacher also, sadly enough).

    2x^2+4x+40=3x^2-2x


    And by the way. It would be extreamly nice if you could help me out two factorizing problems also:

    1. 2x+2a2b(x+a)

    2. a^(x+2)-a^(2x)
    start new problems with a new post, please ... no more than 3 in any one post.
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