- #1
cpyap
- 13
- 0
Homework Statement
Test if the infinite series converge or diverge.
Homework Equations
[tex]
\sum_{n=1}^{\infty}\frac{4n+3}{n(n+1)(n+2)}
[/tex]
The Attempt at a Solution
I tried Ratio test:
[tex]a_{n+1} = \frac{4n+7}{(n+1)(n+2)(n+3)}[/tex]
[tex]a_{n} = \frac{4n+3}{n(n+1)(n+2)}[/tex]
[tex]\left|\frac{a_{n+1}}{a_{n}}\right| = \frac{4n+7}{(n+1)(n+2)(n+3)} \times \frac{n(n+1)(n+2)}{4n+3}
= \frac{n(4+7n)}{(n+3)(4n+3)}
= \frac{4n^{2}+7n}{4n^{2}+15n+9}[/tex]
[tex]lim_{n\rightarrow\infty} \left|\frac{a_{n+1}}{a_{n}}\right| = lim_{n\rightarrow\infty} \frac{4+\frac{7}{n}}{4+\frac{15}{n}+\frac{9}{n^{2}}} = \frac{4}{4} = 1[/tex]
The answer is inconclusive, and I can't seem to think of any other test yet.
Anyone can help me with this?
I will much appreciate it. Thanks!
Last edited: