Math  /  Calculus

QuestionGiven the series: k=6[1k1k+1]\sum_{k=6}^{\infty}\left[\frac{1}{k}-\frac{1}{k+1}\right] does this series converge or diverge? converges diverges 0
If the series converges, find the sum of the series: k=6[1k1k+1]=\sum_{k=6}^{\infty}\left[\frac{1}{k}-\frac{1}{k+1}\right]= \square (If the series diverges, just leave this second box blank.) Question Help: Video Message instructor

Studdy Solution

STEP 1

1. The series given is a telescoping series.
2. A telescoping series is one where most terms cancel out, leaving a finite number of terms.
3. We need to determine if the series converges and, if so, find the sum.

STEP 2

1. Identify the nature of the series.
2. Analyze the series to determine convergence.
3. Calculate the sum of the series if it converges.

STEP 3

Identify the nature of the series. The series is given by:
k=6[1k1k+1] \sum_{k=6}^{\infty}\left[\frac{1}{k}-\frac{1}{k+1}\right]
This is a telescoping series because each term can be written as the difference of two fractions, and many terms will cancel each other out.

STEP 4

To determine convergence, examine the partial sums of the series. The n n -th partial sum Sn S_n is:
Sn=k=6n[1k1k+1] S_n = \sum_{k=6}^{n}\left[\frac{1}{k}-\frac{1}{k+1}\right]
Write out the first few terms to see the pattern:
Sn=(1617)+(1718)++(1n1n+1) S_n = \left(\frac{1}{6} - \frac{1}{7}\right) + \left(\frac{1}{7} - \frac{1}{8}\right) + \ldots + \left(\frac{1}{n} - \frac{1}{n+1}\right)
Notice that all intermediate terms cancel out, leaving:
Sn=161n+1 S_n = \frac{1}{6} - \frac{1}{n+1}
As n n \to \infty , the term 1n+10 \frac{1}{n+1} \to 0 .

STEP 5

Since the limit of the partial sum Sn S_n as n n \to \infty exists and is finite, the series converges.
limnSn=160=16 \lim_{n \to \infty} S_n = \frac{1}{6} - 0 = \frac{1}{6}

STEP 6

Since the series converges, the sum of the series is:
k=6[1k1k+1]=16 \sum_{k=6}^{\infty}\left[\frac{1}{k}-\frac{1}{k+1}\right] = \frac{1}{6}
The series converges, and the sum is:
16 \boxed{\frac{1}{6}}

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