(adsbygoogle = window.adsbygoogle || []).push({}); sum question.........

i have b_k=a_(n_(k)+1)+...+a_(n_(k+1))

c_k=b_1+...+b_k

let us suppose that for every term in b_k has the same sign and that the sum b_k (from n=1 to infinity) converges.

S_n=a_1+...+a_n

and n belongs to {n_k+1,...,n_(k+1)}

then i need to show that

|S_n-c_n|=|a_(n_(k)+1)+...+a_n|

i tried just opened it, and it looked disastrous ( if that's even a word in the anglo-american lexicon).

anyway, your help is appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Sum question.

**Physics Forums | Science Articles, Homework Help, Discussion**