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    So i've been bumbling my way through my problem sheet for this week and the last part of the problem needs me to expand a couple of brackets, for the life of me I can't remember how!
    I need to expand
    (1-\frac{s}{r})^{-2} + (1+\frac{s}{r})^{-2} - 2

    I'm reasonably confident i could do the expansion for -2 if someone asked me but those brackets are messing me up.
    The final answer (after ignoring higher order terms) should only have something containing a r^{-2} term
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    (Original post by radiator0505)
    So i've been bumbling my way through my problem sheet for this week and the last part of the problem needs me to expand a couple of brackets, for the life of me I can't remember how!
    I need to expand
    (1-\frac{s}{r})^{-2} + (1+\frac{s}{r})^{-2} - 2

    I'm reasonably confident i could do the expansion for -2 if someone asked me but those brackets are messing me up.
    The final answer (after ignoring higher order terms) should only have something containing a r^{-2} term
    http://www.mathsrevision.net/alevel/pages.php?page=4
 
 
 
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