1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I think this is simple but I just cant work out how!

  1. Apr 28, 2010 #1
    how does [tex]\frac{1/a -1/b}{1/a+1/b}= \frac{b-a}{b+a}[/tex]

    Ive been trying to work this out for ages

  2. jcsd
  3. Apr 28, 2010 #2
    It's simple algebra. Here's a few hints.

    The right hand side, as given, is this:

    [tex]\frac{\frac{1}{a} - \frac{1}{b}}{\frac{1}{a} + \frac{1}{b}}[/tex]

    But this can be written more clearly as:

    [tex](\frac{1}{a} - \frac{1}{b})(\frac{1}{a} + \frac{1}{b})^{-1}[/tex]

    From there, apply algebraic operations to this expression until it equals the right hand side.
  4. Apr 28, 2010 #3
    Think about what value you need to multiply the left hand side with to make it equal the right hand side.
  5. Apr 28, 2010 #4
    Multiply by ab in both the numerator and the denominator. This is multiplying by one.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: I think this is simple but I just cant work out how!
  1. I just cant get it (Replies: 14)

  2. How do I work this out? (Replies: 28)