Goal: Find the sum of a geometric or telescoping series, and apply the [tex]$n$[/tex]th term test.

Task: Fill in the following blanks.

- A sequence is a \_\_\_\_\_ of numbers.
- A series is a \_\_\_\_\_ of numbers. A series converges if its \_\_\_\_\_ has a limit.
- The nth term test tells us that the series [tex]\sum_{n=1}^{\infty} a_n[/tex] \_\_\_\_\_ if [tex]\lim _{n \to \infty} a_n \neq 0[/tex] and if [tex]\lim _{n \to \infty} a_n = 0[/tex] it tells us \_\_\_\_\_

1. Determine whether the series [tex]\sum_{n=5}^{\infty}\left(1+\frac{1}{n}\right)^n[/tex] converges or diverges. If it converges, find the sum.

Hint: Assume it has some limit [tex]L[/tex] and then take ln of both sides of the equality.



Answer :

Sure, let's examine this step-by-step:

0. Fill in the blanks.

- A sequence is a list of numbers.
- A series is a sum of numbers. A series converges if its partial sum has a limit.
- The nth term test tells us that the series [tex]\(\sum_{n=1}^{\infty} a_n\)[/tex] diverges if [tex]\(\lim_{n \to \infty} a_n \neq\)[/tex] 0 and if [tex]\(\lim_{n \to \infty} a_n =\)[/tex] 0 it tells us nothing conclusive about the series' convergence.

1. Determine whether the series [tex]\(\sum_{n=5}^{\infty}\left(1+\frac{1}{n}\right)^n\)[/tex] converges or diverges. If it converges, find the sum.

To determine whether the series converges or diverges, we will use the nth term test.

The nth term [tex]\( a_n \)[/tex] of the series is given by [tex]\( a_n = \left(1 + \frac{1}{n}\right)^n \)[/tex].

First, we need to find the limit of [tex]\( a_n \)[/tex] as [tex]\( n \)[/tex] approaches infinity:

[tex]\[ \lim_{n \to \infty} \left(1 + \frac{1}{n}\right)^n \][/tex]

It is known that:

[tex]\[ \lim_{n \to \infty} \left(1 + \frac{1}{n}\right)^n = e \][/tex]

where [tex]\( e \approx 2.718281828459045 \)[/tex].

So,

[tex]\(\lim_{n \to \infty} \left(1+\frac{1}{n}\right)^n = 2.718281828459045\)[/tex].

According to the nth term test, if the limit of [tex]\( a_n \)[/tex] as [tex]\( n \)[/tex] approaches infinity is not zero, the series diverges.

Since [tex]\( \lim_{n \to \infty} \left(1 + \frac{1}{n}\right)^n = e \approx 2.718281828459045 \neq 0 \)[/tex],

the series [tex]\(\sum_{n=5}^{\infty} \left(1 + \frac{1}{n}\right)^n\)[/tex] diverges.