Mister Exam
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- Fourier series step by step
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- Product of series
-
How to use it?
- Sum of series:
-
1/((3n-2)(3n+1))
-
3/(n(n+2))
-
(n+1)/5^n
-
6/9n^2+12n-5
-
Identical expressions
- one /(3n+ one)(3n+ four)
- 1 divide by (3n plus 1)(3n plus 4)
- one divide by (3n plus one)(3n plus four)
- 1/3n+13n+4
- 1 divide by (3n+1)(3n+4)
-
Similar expressions
- 1/((3n+1)(3n+4))
- 1/((3n+1)*(3n+4))
- 1/(3n+1)(3n-4)
- 1/(3*n+1)(3*n+4)
- 1/(3*n+1)*(3n+4)
- 1/(3n-1)(3n+4)
- 1/(3*n+1)*(3*n+4)
Sum of series 1/(3n+1)(3n+4)
The solution
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oo ___ \ ` \ 3*n + 4 ) ------- / 3*n + 1 /__, n = 1
$$\sum_{n=1}^{\infty} \frac{3 n + 4}{3 n + 1}$$
Sum((3*n + 4)/(3*n + 1), (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\frac{3 n + 4}{3 n + 1}$$
It is a series of species
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
In this case
$$a_{n} = \frac{3 n + 4}{3 n + 1}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{\left(3 n + 4\right)^{2}}{\left(3 n + 1\right) \left(3 n + 7\right)}\right)$$
Let's take the limit
we find
$$\frac{3 n + 4}{3 n + 1}$$
It is a series of species
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
In this case
$$a_{n} = \frac{3 n + 4}{3 n + 1}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{\left(3 n + 4\right)^{2}}{\left(3 n + 1\right) \left(3 n + 7\right)}\right)$$
Let's take the limit
we find
True
False
The rate of convergence of the power series
Numerical answer
The series diverges
The graph
Examples of finding the sum of a series
- The Sum of the Power Series
x^n/n
(x-1)^n
- Factorial
1/2^(n!)
n^2/n!
x^n/n!
k!/(n!*(n+k)!)
- Flint Hills Series
csc(n)^2/n^3
- Basel problem
1/n^2
1/n^4
1/n^6
- Harmonic series
1/n
- Grandi's series
(-1)^n
- Alternating series
(-1)^(n + 1)/n
(n + 2)*(-1)^(n - 1)
(3*n - 1)/(-5)^n
(-1)^(n - 1)*n/(6*n - 5)
- Newton–Mercator series
(-1)^(n + 1)/n*x^n
- Exam the series for convergence
(3*n - 1)/(-5)^n