proof of Abel’s test for convergence

Let $b$ be the limit of $\{b_{n}\}$ and let $d_{n}=b_{n}-b$ when $\{b_{n}\}$ is decreasing and $d_{n}=b-b_{n}$ when $\{b_{n}\}$ is increasing. By Dirichlet’s convergence test, $\sum a_{n}d_{n}$ is convergent and so is $\sum a_{n}b_{n}=\sum a_{n}(b\pm d_{n})=b\sum a_{n}\pm\sum a_{n}d_{n}$ .

Title	proof of Abel’s test for convergence
Canonical name	ProofOfAbelsTestForConvergence
Date of creation	2013-03-22 13:19:56
Last modified on	2013-03-22 13:19:56
Owner	lieven (1075)
Last modified by	lieven (1075)
Numerical id	4
Author	lieven (1075)
Entry type	Proof
Classification	msc 40A05