# Convergence of a series help

1. Oct 31, 2013

### K.QMUL

1. The problem statement, all variables and given/known data

Determine whether the following are convergent, divergent or oscillating.

2. Relevant equations

3. The attempt at a solution

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Last edited: Oct 31, 2013
2. Oct 31, 2013

### pasmith

You haven't applied the ratio test correctly. You have
$$\lim_{i \to \infty} \left|\frac{a_{i+1}}{a_i}\right| = \lim_{i \to \infty} \left(\frac{i + 1}{i}\right)^2 e^{-K}$$
which is correct. But then you don't try to find the limit, which is what you need to apply the ratio test.

3. Oct 31, 2013

### K.QMUL

How would I go about finding the limit?

4. Oct 31, 2013

### dirk_mec1

i+1~i.

5. Oct 31, 2013

### K.QMUL

Mmmm.. still not sure, am I going about it in the right direction, does it seem divergent?

6. Oct 31, 2013

### Staff: Mentor

Rather than guess whether the series is divergent or convergent, why don't you finish your work on the limit?

7. Oct 31, 2013

### K.QMUL

I thought I had finished, is there something im missing?

8. Oct 31, 2013

### dirk_mec1

Can you find the limit of post #2?