Page 1 of 2 12 LastLast
Results 1 to 15 of 19

Thread: Need help re-arranging an equation!

  1. #1
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Need help re-arranging an equation!

    Hey all I need some help re-arranging this equation so I can find z here it is:

    also is w^2/wn^2 the same as (w/wn)^2? so I could replace w^2/wn^2 with say r^2?

    x= (w^2/wn^2) / (sqrt( {1-w^2/wn^2}^2 + {2*z*w/wn}^2))

    So I have the value for x and I need to find the value of z. I have had a couple of goes at it and I am honestly not sure if what I am doing is right or not.

    Thanks for any and all assistance in advance!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member rowe's Avatar
    Joined
    Jul 2009
    Posts
    89

    Re: Need help re-arranging an equation!

    $\displaystyle \frac{w^2}{(wn)^2} = \frac{w}{wn} \cdot \frac{w}{wn} = \left(\frac{w}{wn}\right)^2$, if that helps you to simplify. You can probably see it can be further simplified.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    Awesome I thought so! Thanks rowe, where do I go first? Do I get rid of the square root or can I take the entire bottom half of the equation over and times by x ?

    $\displaystyle x={r^2}/{sqrt( (1-r^2)^2 + (2*z*r)^2)}$
    Last edited by Rhys101; Jun 18th 2012 at 11:04 PM.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    will the sqrt just cancel out the squares on the brackets?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    crap= given wrong equation to start with- real one is here:

    $\displaystyle x= (M*R/m)*(r^2) / (sqrt( {1-r^2}^2 + {2*z*r}^2))$
    Last edited by Rhys101; Jun 18th 2012 at 11:24 PM.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member rowe's Avatar
    Joined
    Jul 2009
    Posts
    89

    Re: Need help re-arranging an equation!

    So your equation is, $\displaystyle x = \frac{M\cdot\frac{R}{m}\cdot r^2}{\sqrt{{(1-r^2)}^2+2zr^2}}$, and you need to solve for $\displaystyle z$?
    Last edited by rowe; Jun 19th 2012 at 12:37 AM.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    oh, poo, the M*R/m was just set next to the other equation no multiplication sign but a gap between the horizontal divide line if that makes sense? I am sorry
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Member rowe's Avatar
    Joined
    Jul 2009
    Posts
    89

    Re: Need help re-arranging an equation!

    No worries; did you mean:

    $\displaystyle x = M\cdot\frac{R}{m}\cdot\frac{r^2}{\sqrt{{(1-r^2)}^2+2zr^2}}$ ?

    You can actually hover over any equation to see the TeX being used. It takes a bit of learning to write what you want but it definitely speeds things up once you know how to write stuff properly.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    If that is the same as $\displaystyle (M*R)/m$ then thats the one! I'm sorry! Slowly learning this Latex thingimy. Oh, and the 2*z*r was in brackets then squared so : $\displaystyle (2*z*r)^2$
    I hope that works!


    Follow Math Help Forum on Facebook and Google+

  10. #10
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    Sorry rowe, thanks for your patience with me!
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Member rowe's Avatar
    Joined
    Jul 2009
    Posts
    89

    Re: Need help re-arranging an equation!

    Cool, so we have:

    $\displaystyle x = \frac{MR}{m}\cdot\frac{r^2}{\sqrt{{(1-r^2)}^2+{(2zr)}^2}}$ and we need to solve for $\displaystyle z$. The first step is to remove the square root from the denominator. Do you know how to do this?
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    I am not sure, no sorry, I thought that the squares on the brackets underneath the sqrt would cancel?
    Follow Math Help Forum on Facebook and Google+

  13. #13
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    Anyone else?
    Follow Math Help Forum on Facebook and Google+

  14. #14
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    76
    Awards
    1

    Re: Need help re-arranging an equation!

    Quote Originally Posted by Rhys101 View Post
    I am not sure, no sorry, I thought that the squares on the brackets underneath the sqrt would cancel?
    No. There are two terms under the radical, and we cannot split a radical over addition. So

    $\displaystyle \sqrt{a^2} = |a|$

    but it is not generally true that

    $\displaystyle {\color{red}\sqrt{a^2 + b^2} = |a| + |b|}\quad\leftarrow$ Don't do this.

    To get rid of the square root, you'll need to square both sides of the equation.
    Follow Math Help Forum on Facebook and Google+

  15. #15
    Junior Member
    Joined
    Jun 2012
    From
    Australia
    Posts
    36

    Re: Need help re-arranging an equation!

    Ok cool so do I need to flip the equation to square everything? so I get $\displaystyle (1/x)^2$? and $\displaystyle (m/MR)^2$? DO I need to square the r^2 on the bottom as well, If I have flipped the equation?
    Follow Math Help Forum on Facebook and Google+

Page 1 of 2 12 LastLast

Similar Math Help Forum Discussions

  1. Re-arranging an equation.
    Posted in the Algebra Forum
    Replies: 9
    Last Post: Feb 13th 2011, 07:25 PM
  2. Re-arranging a log equation.
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: Oct 24th 2010, 07:38 PM
  3. Re-arranging an equation
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 5th 2010, 03:22 PM
  4. Re arranging an equation.
    Posted in the Algebra Forum
    Replies: 2
    Last Post: Aug 27th 2009, 06:26 PM
  5. Re-arranging equation
    Posted in the Algebra Forum
    Replies: 5
    Last Post: Mar 29th 2009, 06:21 AM

Search Tags


/mathhelpforum @mathhelpforum