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Math Help - Can anyone help to rearrange this equation??

  1. #1
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    Can anyone help to rearrange this equation??

    Hi,I'm an engineering student, trying to re-arrange an equation but struggling, my tutor can't do it either!! I'd appreciate your advice or solutions. I have the following equation and need to rearrange in terms of y. c(x/y+ xR/y)= 245.6*S^(-0.77)*(xR/y)^0.68 When we try we end up either cancelling y out all together or being unable to get all the y's on one side.Thanks in advance!!Lisa
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  2. #2
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    Re: Can anyone help to rearrange this equation??

    Real solutions :

    y_{1,2}=\pm \left(  3.392628978 \cdot 10^{-8} \cdot\,x{S}^{{\frac {231}{100}}}{c}^{4} \left(  1.0+R \right) ^{4}{R}^{-2}{\frac {1}{\sqrt [8]{{c}^{7} \left(  1.0+R \right) ^{7}R{S}^{-{\frac {77}{100}}}}}} \right)
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  3. #3
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    Re: Can anyone help to rearrange this equation??

    Thanks very much for the quick response!Apologies my maths is not as good as it could be. I don't understand what y1,2 means before the '=' and sorry to be a pain but could you explain how you got to this answer, I'd really like to understand for myself, in case I have to do anything similar in the future.
    Last edited by lah183; May 8th 2012 at 07:33 AM.
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  4. #4
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    Re: Can anyone help to rearrange this equation??

    Quote Originally Posted by lah183 View Post
    I have the following equation and need to rearrange in terms of y. c(x/y+ xR/y)= 245.6*S^(-0.77)*(xR/y)^0.68
    let \frac{x}{y} = z

    c(z + Rz) = 245.6s^{-0.77} \cdot (Rz)^{0.68}

    z(c + Rc) = 245.6s^{-0.77} \cdot R^{0.68}z^{0.68}

    \frac{z}{z^{0.68}} = \frac{245.6s^{-0.77}}{c+Rc}

    z^{0.32} = \frac{245.6s^{-0.77}}{c+Rc}

    \frac{x^{0.32}}{y^{0.32}} = \frac{245.6s^{-0.77}}{c+Rc}

    \frac{y^{0.32}}{x^{0.32}} = \frac{c+Rc}{245.6s^{-0.77}}

    y^{0.32} = \frac{cx^{0.32}(1+R)}{245.6s^{-0.77}}

    y = \left[\frac{cx^{0.32}(1+R)}{245.6s^{-0.77}}\right]^{\frac{25}{8}}
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    Re: Can anyone help to rearrange this equation??

    Thanks Skeeter, your answer is really easy to understand. I appreciate you taking your time to show the workings out. Only thing is I think R^0.68 got lost along the way (from Row 3 of your calculation). When I re-work this I get the answer the same as you but with 245.6x^-0.77 x R^0.68 on the bottom of the fraction. Hope that's correct?
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  6. #6
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    Re: Can anyone help to rearrange this equation??

    That would be correct. I forgot to transfer R^(0.68) and , of course, each follow on step was a copy/paste from the previous step. But, you got the idea.
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  7. #7
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    Re: Can anyone help to rearrange this equation??

    i know some tutors who can do this: Tutor Universe
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