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Integration algabriac manipulation problem

  1. Sep 15, 2015 #1
    Hello there,

    I was wondering if someone might be able to help me out with some intermediate steps please. I can't see how
    $$f_{tt} =-\int_{r_0}^0 \left(\frac{2Gm_0}{r} - \frac{2Gm_0}{r_0}\right)^{-\frac{1}{2}} dr$$
    $$f_{tt} =- \left(\frac{2Gm_0}{r_0}\right)^{-\frac{1}{2}}\int_{r_0}^0\left(\frac{r_0}{r}-1\right)^{-\frac{1}{2}}dr$$
    I've been wracking my brain over this and can't see how it's been done. I originally thought that the fraction containing all the constants was pulled out somehow but this can't be possible since
    $$(A+B)^n \neq A^n + B^n$$
    I would be very grateful if someone could point me in the right direction.


  2. jcsd
  3. Sep 15, 2015 #2
    You are correct with ##\left( A + B \right)^n \neq A^n +B^n##.
    That's not what we are using here.

    We use that ##\left( C\cdot A + C \cdot B\right)^n = \left[ C\left(A+b\right)\right]^n = C^n\left(A+B\right)^n##
  4. Sep 15, 2015 #3
    Excellent! Thank you so much. I've just had a scribble around and got it sussed now. :smile:


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