1. **Stating the problem:** Find the limit $$\lim_{n \to \infty} \frac{1 + r + r^2 + \cdots + r^n}{n + r} - \frac{n}{r}$$ where $r$ is a constant.
2. **Recall the formula for the sum of a geometric series:**
$$\sum_{k=0}^n r^k = \frac{1 - r^{n+1}}{1 - r} \quad \text{for } r \neq 1$$
3. **Rewrite the numerator using the geometric series sum:**
$$1 + r + r^2 + \cdots + r^n = \frac{1 - r^{n+1}}{1 - r}$$
4. **Substitute into the limit expression:**
$$\lim_{n \to \infty} \frac{\frac{1 - r^{n+1}}{1 - r}}{n + r} - \frac{n}{r} = \lim_{n \to \infty} \frac{1 - r^{n+1}}{(1 - r)(n + r)} - \frac{n}{r}$$
5. **Analyze the behavior as $n \to \infty$ depending on $|r|$:**
- If $|r| < 1$, then $r^{n+1} \to 0$.
- If $|r| > 1$, then $r^{n+1} \to \infty$ or diverges.
- If $r = 1$, the sum is $n+1$.
6. **Case 1: $|r| < 1$**
$$\lim_{n \to \infty} \frac{1 - 0}{(1 - r)(n + r)} - \frac{n}{r} = \lim_{n \to \infty} \frac{1}{(1 - r)(n + r)} - \frac{n}{r}$$
The first term tends to 0 as $n \to \infty$, so the limit behaves like
$$- \frac{n}{r} \to -\infty$$
7. **Case 2: $r = 1$**
Sum is $n+1$, so
$$\lim_{n \to \infty} \frac{n+1}{n+1} - \frac{n}{1} = \lim_{n \to \infty} 1 - n = -\infty$$
8. **Case 3: $|r| > 1$**
Since $r^{n+1}$ dominates,
$$\frac{1 - r^{n+1}}{(1 - r)(n + r)} \approx \frac{-r^{n+1}}{(1 - r)(n + r)}$$
As $n \to \infty$, numerator grows exponentially, denominator grows linearly, so the fraction tends to $\pm \infty$ depending on $r$.
9. **Conclusion:**
- For $|r| \leq 1$, the limit diverges to $-\infty$.
- For $|r| > 1$, the limit diverges to infinity or negative infinity depending on the sign of $r^{n+1}$.
**Final answer:** The limit does not converge to a finite value for any $r$.
Limit Series 8C97A3
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