Chatterbox AI Powered Learning

If S = sigma from n=2 to infinity of (3n^2 + 1) divided by (n^2 - 1) cubed, then 16S is:

Question

If S=n=23n2+1(n21)3S=\sum_{n=2}^{\infty} \frac{3n^2+1}{(n^2-1)^3} then 16S16S is:

Answer

****:

Given:

S=n=23n2+1(n21)3 S = \sum_{n=2}^{\infty} \frac{3n^2 + 1}{(n^2 - 1)^3}

We start by recognizing that:

(n21)3=(n1)3(n+1)3 (n^2 - 1)^3 = (n-1)^3 (n+1)^3

Additionally:

(n+1)3(n1)3=6n2+2 (n+1)^3 - (n-1)^3 = 6n^2 + 2

Now, we can express the series as follows:

S=n=212((n+1)3(n1)3(n+1)3(n1)3) S = \sum_{n=2}^{\infty} \frac{1}{2} \left(\frac{(n+1)^3 - (n-1)^3}{(n+1)^3 (n-1)^3}\right)

Rewriting the sum, we get:

S=12n=2(1(n1)31(n+1)3) S = \frac{1}{2} \sum_{n=2}^{\infty} \left( \frac{1}{(n-1)^3} - \frac{1}{(n+1)^3} \right)

This can be expanded as a telescoping series:

S=12((113133)+(123143)+(133153)+) S = \frac{1}{2} \left( \left( \frac{1}{1^3} - \frac{1}{3^3} \right) + \left( \frac{1}{2^3} - \frac{1}{4^3} \right) + \left( \frac{1}{3^3} - \frac{1}{5^3} \right) + \ldots \right)

The terms 133,143,\frac{1}{3^3}, \frac{1}{4^3}, \ldots cancel out in the series, leaving us with:

S=12(113+123) S = \frac{1}{2} \left( \frac{1}{1^3} + \frac{1}{2^3} \right)

Simplifying further:

S=12(1+18)=12(98)=916 S = \frac{1}{2} \left( 1 + \frac{1}{8} \right) = \frac{1}{2} \left( \frac{9}{8} \right) = \frac{9}{16}

Thus,

16S=16916=9 16S = 16 \cdot \frac{9}{16} = 9

Therefore, the value of 16S16S is:

9 \boxed{9}

Follow-up Questions:

Related Questions

See how Chatterbot AI can help you succeed

Hi there! What can I help you learn today?

Click here to learn something new with Chatterbox AI Tutor.

Chatterbox

AI Tutor