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Posted by on Tuesday, August 28, 2012 at 10:48am.

Rearrange r+s/8s=r-s/8n to make r the subject.


OK, I have started by rearranging the formula:

8n(r+s)=8s(r-s)

What do I do next?

  • algebra - , Tuesday, August 28, 2012 at 11:02am

    so you must have meant
    (r+s)/(8s)=(r-s)/(8n)

    so 8n(r+s)=8s(r-s) is correct so far. Le'ts expand it
    8nr + 8rs = 8rs - 8s^2
    8nr = -8s^2
    nr = -s^2
    r = -s^2/n

  • algebra - , Tuesday, August 28, 2012 at 11:05am

    thank you!

  • algebra - , Tuesday, August 28, 2012 at 11:10am

    just realised, should the second line be
    8nr+8NS?, not 8rs?

  • algebra - , Tuesday, August 28, 2012 at 11:15am

    just realised, should the second line be
    8nr+8NS?, not 8rs?.........

  • algebra - , Tuesday, August 28, 2012 at 11:18am

    your are right, good for you to notice
    I have to mind my n, r and s's

    8nr + 8ns = 8rs - 8s^2
    collect all terms containing r to one side
    8nr - 8rs = -8s^2 - 8ns
    factor out the r
    r(8n - 8s) = -8s^2 - 8ns
    r = (-8s^2 - 8ns)/(8n - 8s)
    divide top and bottom by 8 on the RS
    r = (-s^2 - ns)/(n-s)
    or -s(s+n)/(n-s)

  • algebra - , Tuesday, August 28, 2012 at 11:23am

    great, that makes sense, thanks

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