Math Problem Statement

sigma(infinity and n=5)(1/(x+1)-1/(n+2)) telescopic

Solution

To evaluate the telescoping sum:

n=5(1n+11n+2)\sum_{n=5}^{\infty} \left( \frac{1}{n+1} - \frac{1}{n+2} \right)

This is a telescoping series, where terms cancel out as we expand the summation.

Step-by-step solution:

  1. Write out the first few terms of the sum: (1617)+(1718)+(1819)+\left( \frac{1}{6} - \frac{1}{7} \right) + \left( \frac{1}{7} - \frac{1}{8} \right) + \left( \frac{1}{8} - \frac{1}{9} \right) + \dots

  2. Notice the cancellation of intermediate terms:

    • The 17\frac{1}{7} in the first term cancels with 17-\frac{1}{7} in the second term.
    • The 18\frac{1}{8} in the second term cancels with 18-\frac{1}{8} in the third term, and so on.
  3. As the sum progresses, all the terms cancel out except for the very first term of the series and the limiting term as nn \to \infty.

  4. At the limit as nn \to \infty: limn1n+2=0\lim_{n \to \infty} \frac{1}{n+2} = 0

  5. Therefore, the sum simplifies to: n=5(1n+11n+2)=16\sum_{n=5}^{\infty} \left( \frac{1}{n+1} - \frac{1}{n+2} \right) = \frac{1}{6}

Final answer:

16\boxed{\frac{1}{6}}

Would you like further details or have any questions on this? Here are 5 related questions to expand this topic:

  1. How do you recognize a telescoping series in general?
  2. What are other examples of telescoping series?
  3. What happens when the series does not converge?
  4. Can you apply telescoping sums to finite limits (non-infinite)?
  5. What other types of series can be summed analytically?

Tip: Always check the behavior of the terms as nn \to \infty to confirm whether a telescoping series converges or diverges.

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Math Problem Analysis

Mathematical Concepts

Series and Sequences
Telescoping Series
Limits

Formulas

Sum of a telescoping series: \( \sum_{n=5}^{\infty} \left( \frac{1}{n+1} - \frac{1}{n+2} \right) \)
Limit as n approaches infinity: \( \lim_{n \to \infty} \frac{1}{n+2} = 0 \)

Theorems

Telescoping Series Theorem
Limit Theorem

Suitable Grade Level

College Level or Advanced High School