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steelphantom is offline
Apr29-08, 11:19 AM
P: 159
Quote Quote by Dick View Post
Sorry! That's wrong. I'm clearly asleep at the wheel. That's convergence for sequences. And this sort of argument only shows that the partial sums are bounded, not that they converge. Do you know the Dirichlet convergence test?
I don't know that one. But the comparison test in my book says the following:

Let [tex]\sum[/tex]an be a series where an >=0 for all n.
(i) If [tex]\sum[/tex]an converges and |bn| <= an for all n, then [tex]\sum[/tex]bn converges.

If I let an = anRn, this is >=0 for all n. And if I let bn = an(-R)n, then I have |bn| <= an for all n, so the series converges, right? What's wrong with this statement?