Math Problem Statement

Evaluate the infinite series \( \sum_{n=1}^\infty \frac{(-1)^n 10^n (x - 10)^n}{n!} \).

Solution

The given expression is:

n=1(1)n10n(x10)nn!.\sum_{n=1}^{\infty} \frac{(-1)^n 10^n (x - 10)^n}{n!}.

This series looks like a modification of the Taylor or Maclaurin series for the exponential function. Let me analyze and simplify it.

Step-by-Step Solution:

  1. General Form of the Exponential Series: Recall that the Taylor expansion for exe^x around x=0x = 0 is: ex=n=0xnn!.e^x = \sum_{n=0}^\infty \frac{x^n}{n!}.

  2. Recognizing the Structure: The given series has the term (1)n10n(x10)n(-1)^n 10^n (x - 10)^n. If we rewrite it, we get: n=1[(1)(10)(x10)]nn!.\sum_{n=1}^\infty \frac{\left[(-1)(10)(x-10)\right]^n}{n!}. Let z=10(x10)z = -10(x - 10). Substituting this into the series, we have: n=1znn!.\sum_{n=1}^\infty \frac{z^n}{n!}.

  3. Simplifying the Summation: This summation can be related to the Taylor series of eze^z. Recall: ez=n=0znn!.e^z = \sum_{n=0}^\infty \frac{z^n}{n!}. Since our series starts at n=1n = 1 (not n=0n = 0), we can write: n=1znn!=ez1.\sum_{n=1}^\infty \frac{z^n}{n!} = e^z - 1.

  4. Substitute Back zz: Substitute z=10(x10)z = -10(x - 10) into ez1e^z - 1: n=1(1)n10n(x10)nn!=e10(x10)1.\sum_{n=1}^\infty \frac{(-1)^n 10^n (x - 10)^n}{n!} = e^{-10(x - 10)} - 1.

Final Answer:

n=1(1)n10n(x10)nn!=e10(x10)1.\sum_{n=1}^\infty \frac{(-1)^n 10^n (x - 10)^n}{n!} = e^{-10(x - 10)} - 1.

Would you like a detailed explanation of how the substitution and simplification work? Let me know!


Related Questions:

  1. What is the Taylor series of exe^x centered at a different point aa?
  2. How does the structure of alternating series affect convergence?
  3. What are some real-world applications of exponential functions and series expansions?
  4. How does the factorial in the denominator ensure the series converges for all xx?
  5. Can this series representation help in numerical approximations of e10(x10)1e^{-10(x - 10)} - 1?

Tip:

When working with Taylor series, always try to identify the general pattern of coefficients to relate it to standard series expansions like exe^x, sin(x)\sin(x), or cos(x)\cos(x). This saves time and simplifies the solution!

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Math Problem Analysis

Mathematical Concepts

Taylor Series
Exponential Functions
Series Expansion

Formulas

General exponential function expansion: \( e^x = \sum_{n=0}^\infty \frac{x^n}{n!} \)
Shifted series transformation: \( \sum_{n=1}^\infty \frac{z^n}{n!} = e^z - 1 \)

Theorems

Exponential Function Theorem
Properties of Taylor Series

Suitable Grade Level

Undergraduate Math (Calculus)