Can anyone help to rearrange this equation??

• May 8th 2012, 06:01 AM
lah183
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
• May 8th 2012, 06:17 AM
princeps
Re: Can anyone help to rearrange this equation??
Real solutions :

$y_{1,2}=\pm \left( 3.392628978 \cdot 10^{-8} \cdot\,x{S}^{{\frac {231}{100}}}{c}^{4} \left( 1.0+R \right) ^{4}{R}^{-2}{\frac {1}{\sqrt [8]{{c}^{7} \left( 1.0+R \right) ^{7}R{S}^{-{\frac {77}{100}}}}}} \right)$
• May 8th 2012, 06:30 AM
lah183
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.
• May 8th 2012, 10:57 AM
skeeter
Re: Can anyone help to rearrange this equation??
Quote:

Originally Posted by lah183
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 $\frac{x}{y} = z$

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

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

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

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

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

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

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

$y = \left[\frac{cx^{0.32}(1+R)}{245.6s^{-0.77}}\right]^{\frac{25}{8}}$
• May 9th 2012, 12:27 AM
lah183
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?
• May 9th 2012, 03:14 AM
skeeter
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.
• Mar 3rd 2013, 06:13 PM
ThomasHornbeck
Re: Can anyone help to rearrange this equation??
i know some tutors who can do this: Tutor Universe