find the Sn of An = (1/n) -(1/n+2)
i got the denominator n^2 + 3n + 2 but can't find the numerator
Hi confusedgirl,
You can write it this way...by placing in the values of n=1, 2, 3, 4, 5...
If you examine this, you will see that virtually all of the terms cancel,
due to the same terms having + and -.
Which terms will be left standing?
Also, what process did you use to calculate your original denominator?
i'm sorry, but i think my question wasn't clear i need to get Sn where
Sn = Sn-1 + An
like
S1 = 1-1/3 = 2/3
S2 = 2/3 +1/2 -1/4 = 11/12
S3= 21/20
S4 = 34/30
i really didn't use any process or technique to get the denominator but just figured it out by trial and error
reduces to
since the last term to cancel is
as a term can only cancel a term 3 places to the right.
as all the other terms cancel.
This will give you Sn for any n, without having to calculate a preceding sum.