Give step-by-step solution with explanation and final answer:
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Give step-by-step solution with explanation and final answer:
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Asked by: Test User 100251
Created at: 2025-05-21 06:54:21
Asked by: Test User 100251
Created at: 2025-05-21 06:54:21
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Let's analyze the given series:
\[
\sum_{n=0}^{\infty} (-1)^n \frac{x^n}{n^2}
\]
We are asked whether it **converges absolutely**, **converges conditionally**, or **diverges**.
---
### **Step 1: Test for Absolute Convergence**
Absolute convergence means we consider:
\[
\sum_{n=0}^{\infty} \left|(-1)^n \frac{x^n}{n^2}\right| = \sum_{n=0}^{\infty} \frac{|x|^n}{n^2}
\]
This is a power series, and for a general \( |x| < 1 \), the terms \(\frac{|x|^n}{n^2}\) resemble a p-series in the denominator times a geometric series in the numerator.
#### **Check for convergence:**
- For \( |x| < 1 \):
- As \( n \to \infty \), \( |x|^n \to 0 \) rapidly.
- \( n^2 \) grows faster than any polynomial in \( n \).
- In fact, for any fixed \( |x| < 1 \), this converges by the **comparison test** to a convergent p-series, since \( \sum \frac{1}{n^2} \) converges, and \( |x|^n \) decays faster than any polynomial grows.
- For \( |x| = 1 \):
- The series becomes \( \sum \frac{1}{n^2} \), which converges (p-series with \( p = 2 > 1 \)).
- Thus, the series converges absolutely for \( |x| \leq 1 \).
- For \( |x| > 1 \):
- \( |x|^n \) grows faster than \( n^2 \), so the terms do **not** approach zero, and the series **diverges**.
---
### **Step 2: Conclusion**
- The given series **converges absolutely** for \( |x| \leq 1 \).
- It **diverges** for \( |x| > 1 \).
---
### **Final Answer**
**The series**
\[
\sum_{n=0}^{\infty} (-1)^n \frac{x^n}{n^2}
\]
**converges absolutely for \( |x| \leq 1 \), and diverges for \( |x| > 1 \).**
---
If you want to specify for a particular value of \( x \), let me know! For example, for \( x = 1 \), the series converges absolutely since it's a p-series with \( p=2 \).
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