1. **Problem statement:** We want to determine for which values of $x$ the series $$\sum_{n=1}^{\infty} \frac{1}{n} \left(1+\frac{1}{x}\right)^n$$ is absolutely convergent, conditionally convergent, or divergent.
2. **Recall the series:** This is a power series in terms of $$a = 1 + \frac{1}{x}$$ with general term $$\frac{1}{n} a^n$$.
3. **Important rule:** The series $$\sum_{n=1}^\infty \frac{a^n}{n}$$ converges if and only if $$|a| \leq 1$$, and it converges absolutely if $$|a| < 1$$. If $$a = -1$$, the series converges conditionally (alternating harmonic series). If $$|a| > 1$$, the series diverges.
4. **Analyze $$a = 1 + \frac{1}{x}$$:**
- Absolute convergence requires $$|1 + \frac{1}{x}| < 1$$.
- Conditional convergence occurs if $$1 + \frac{1}{x} = -1$$.
- Divergence if $$|1 + \frac{1}{x}| > 1$$ and not equal to -1.
5. **Solve absolute convergence inequality:**
$$|1 + \frac{1}{x}| < 1$$
This means:
$$-1 < 1 + \frac{1}{x} < 1$$
Subtract 1 throughout:
$$-2 < \frac{1}{x} < 0$$
6. **Solve inequalities for $$x$$:**
- From $$\frac{1}{x} < 0$$, we get $$x < 0$$.
- From $$\frac{1}{x} > -2$$:
If $$x < 0$$, then multiplying by $$x$$ (negative) reverses inequality:
$$1 > -2x$$
Divide by -2 (negative), reverse inequality:
$$x > -\frac{1}{2}$$
7. **Combine:**
$$-\frac{1}{2} < x < 0$$ for absolute convergence.
8. **Check conditional convergence:**
Set $$1 + \frac{1}{x} = -1$$
$$\frac{1}{x} = -2$$
$$x = -\frac{1}{2}$$
At $$x = -\frac{1}{2}$$, the series is $$\sum \frac{(-1)^n}{n}$$ which converges conditionally.
9. **Check divergence:**
For $$x > 0$$ or $$x \leq -\frac{1}{2}$$ (except $$x = -\frac{1}{2}$$), the series diverges.
**Final answer:**
- Absolutely convergent for $$-\frac{1}{2} < x < 0$$
- Conditionally convergent at $$x = -\frac{1}{2}$$
- Divergent otherwise.
Series Convergence Df6D1D
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