Math Problem Statement

Find the behavior and convergence of the infinite series \( \sum_{n=0}^\infty n! (x + 3)^n \).

Solution

This is an infinite series:
n=0n!(x+3)n\sum_{n=0}^\infty n! (x + 3)^n

Step-by-Step Solution:

  1. Analyze the series terms: Each term in the series is of the form n!(x+3)nn! (x + 3)^n.

  2. Behavior when n=0n = 0: When n=0n = 0: n!(x+3)n=0!(x+3)0=11=1n! (x + 3)^n = 0! (x + 3)^0 = 1 \cdot 1 = 1

    So the first term is 11.

  3. Convergence Test: Since the factorial n!n! grows very fast for n>1n > 1, this series diverges for all x3x \neq -3, because the term n!(x+3)nn! (x + 3)^n grows without bound.

  4. Conclusion: The series diverges for all x3x \neq -3. For x=3x = -3, the series converges trivially to 11, as all terms except the first become 00.


Would you like a detailed explanation of the convergence test, or any other details?


Here are 5 related questions for further exploration:

  1. What is the general form of a factorial, and how does it grow as nn \to \infty?
  2. How can the Ratio Test be applied to determine the convergence of series?
  3. What happens to the series if we replace n!n! with 1n!\frac{1}{n!}?
  4. What is the domain of convergence for power series in general?
  5. Can the series n=0an(x+c)n\sum_{n=0}^\infty a_n (x + c)^n converge for some ana_n? How does ana_n affect convergence?

Tip: When working with infinite series, testing convergence is key to understanding its behavior.

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Math Problem Analysis

Mathematical Concepts

Infinite Series
Factorial Growth
Convergence of Series

Formulas

General Term: n! (x + 3)^n
Convergence Tests: Growth of Factorials, Ratio Test

Theorems

Factorial Growth Properties
Divergence of Series with Unbounded Terms

Suitable Grade Level

Undergraduate Mathematics or Advanced High School (Grades 11-12)