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Old 12-10-07, 06:42 PM   #1
cnickgo
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calc help pretty please

Ok guys im stuck on one correction, and I have to turn this in before I take my exam at noon tommorow. Dealing with series:

the series: sum from n=1 to infinity 1/n3^n
I know it converges (the book says so!), how do I show that and find the upper and lower limits?

Please some bored and benevolent engineer/physicist/mathematician or any other calculus saavy person help me out. I need to move on and study other classes.
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Old 12-10-07, 07:01 PM   #2
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Two hints:

1. Graph it.

2. Plug in some numbers into the equation and note where they seem to converge to.
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Old 12-10-07, 07:46 PM   #3
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What is n3^n? It would be helpful if you would use parentheses or whatever else it took to make it absolutely unambiguous what you're trying to write.

And what have you tried so far?
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Old 12-10-07, 07:58 PM   #4
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Quote:
Originally Posted by jschen View Post
What is n3^n? It would be helpful if you would use parentheses or whatever else it took to make it absolutely unambiguous what you're trying to write.

And what have you tried so far?
sorry 1/ n*(3^n)

I know it's not a geometric series, can't be p-test or ratio rest, i could compare it with most anything but that wouldn't give the specific bounds I need, and as far as the integral-test maple spit out an imaginary answer and I can't find a simple solution to that either.
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Old 12-10-07, 09:52 PM   #5
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is that 1/n 3^n or 1/(n3^n)?
if it's the latter, here's a hint. Your first step is the divergence test. Take the limit.
Why can't you use the ratio test? Work it on paper, and tell me what you get.
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Old 12-10-07, 11:11 PM   #6
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Series with nth term 1/(n*(3^n)) converges by comparison to the geometric series where the nth term is 1/(3^n) because the denominator is larger.

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Old 12-11-07, 05:36 AM   #7
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What the foo is this? I'm just in meager pre-cal, whew.
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Old 12-11-07, 10:12 AM   #8
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Following up. Do the ratio test and take the limit.
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Old 12-11-07, 10:14 AM   #9
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I took my calc II final yesterday. It killed me. Hoping for a passing grade in the class...
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