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# Embarrassingly simple geometric sum question watch

1. I have the sum (1+g/1+r) +(1+g/1+r)^2 + (1+g/1+r)^3 +.....

Using that basic formula from AS 1/1-x with x=1+g/1+r nI get 1+r/r-g instead of the 1+g/r-g I should be getting, baffled as to how I'm not getting it

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2. (Original post by BackToMathsAgain)
I have the sum (1+g/1+r) +(1+g/1+r)^2 + (1+g/1+r)^3 +.....

Using that basic formula from AS 1/1-x with x=1+g/1+r nI get 1+r/r-g instead of the 1+g/r-g I should be getting, baffled as to how I'm not getting it

This was posted from The Student Room's iPhone/iPad App
The sum to infinity of a geometric series is where "a" is the first term and "r" the ratio of terms.

Edit: Also, the expansion of 1/(1-x) is 1+x+x^2....
3. Forgot the a, thanks

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Updated: January 3, 2013
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