Sr Examen

Otras calculadoras

Suma de la serie ((n-2)^3*(x+3)^(2n))/(2n+3)



=

Solución

Ha introducido [src]
  oo                     
____                     
\   `                    
 \           3        2*n
  \   (n - 2) *(x + 3)   
  /   -------------------
 /          2*n + 3      
/___,                    
n = 1                    
$$\sum_{n=1}^{\infty} \frac{\left(n - 2\right)^{3} \left(x + 3\right)^{2 n}}{2 n + 3}$$
Sum(((n - 2)^3*(x + 3)^(2*n))/(2*n + 3), (n, 1, oo))
Radio de convergencia de la serie de potencias
Se da una serie:
$$\frac{\left(n - 2\right)^{3} \left(x + 3\right)^{2 n}}{2 n + 3}$$
Es la serie del tipo
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- serie de potencias.
El radio de convergencia de la serie de potencias puede calcularse por la fórmula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
En nuestro caso
$$a_{n} = \frac{\left(n - 2\right)^{3}}{2 n + 3}$$
y
$$x_{0} = -3$$
,
$$d = 2$$
,
$$c = 1$$
entonces
$$R^{2} = -3 + \lim_{n \to \infty}\left(\frac{\left(n - 2\right)^{2} \left(2 n + 5\right) \left|{n - 2}\right| \left|{\frac{1}{\left(n - 1\right)^{3}}}\right|}{2 n + 3}\right)$$
Tomamos como el límite
hallamos
$$R^{2} = -2$$
$$R = 1.4142135623731 i$$
Respuesta [src]
    //         /              2                         \                         \                                                                                                                                                                                                                                                                                                                          
    ||         |     5*(3 + x)           /   __________\|                         |     //         /                                                 /   __________\ \                    \      //         /                                    /   __________\ \                    \   //         /                                                                  /   __________\\                    \
    ||         |-5 - ----------          |  /        2 ||                         |     ||         |                   4             2               |  /        2 | |                    |      ||         |                    2               |  /        2 | |                    |   ||         |                     4             6              2               |  /        2 ||                    |
    ||       2 |         3        5*atanh\\/  (3 + x)  /|                         |     ||       2 |   -45 - 20*(3 + x)  + 75*(3 + x)        45*atanh\\/  (3 + x)  / |                    |      ||       2 |    -15 + 10*(3 + x)        15*atanh\\/  (3 + x)  / |                    |   ||       2 |   -135 - 305*(3 + x)  + 40*(3 + x)  + 360*(3 + x)       135*atanh\\/  (3 + x)  /|                    |
    ||(3 + x) *|--------------- + ----------------------|                         |     ||(3 + x) *|-------------------------------------- + ------------------------|                    |      ||(3 + x) *|------------------------- - ------------------------|                    |   ||(3 + x) *|------------------------------------------------------ - ------------------------|                    |
    ||         |           4         __________         |                         |     ||         |           6            4            8        __________         |                    |      ||         |           4            6        __________         |                    |   ||         |            8            4            10             6        __________         |                    |
    ||         |    (3 + x)         /        2         4|                         |     ||         |- 8*(3 + x)  + 4*(3 + x)  + 4*(3 + x)        /        2         4|                    |      ||         |- 2*(3 + x)  + 2*(3 + x)        /        2         4|                    |   ||         |- 24*(3 + x)  - 8*(3 + x)  + 8*(3 + x)   + 24*(3 + x)        /        2         4|                    |
    ||         \                  \/  (3 + x)  *(3 + x) /                         |     ||         \                                         4*\/  (3 + x)  *(3 + x) /      |       2|    |      ||         \                            2*\/  (3 + x)  *(3 + x) /      |       2|    |   ||         \                                                         8*\/  (3 + x)  *(3 + x) /      |       2|    |
    ||---------------------------------------------------  for And(x > -4, x < -2)|     ||----------------------------------------------------------------------------  for |(3 + x) | < 1|      ||---------------------------------------------------------------  for |(3 + x) | < 1|   ||--------------------------------------------------------------------------------------------  for |(3 + x) | < 1|
    ||                         5                                                  |     ||                                     5                                                          |      ||                               5                                                   |   ||                                             5                                                                  |
- 8*|<                                                                            | - 6*|<                                                                                                | + 12*|<                                                                                   | + |<                                                                                                                |
    ||                   oo                                                       |     ||                              oo                                                                |      ||                        oo                                                         |   ||                                      oo                                                                        |
    ||                 ____                                                       |     ||                            ____                                                                |      ||                      ____                                                         |   ||                                    ____                                                                        |
    ||                 \   `                                                      |     ||                            \   `                                                               |      ||                      \   `                                                        |   ||                                    \   `                                                                       |
    ||                  \           2*n                                           |     ||                             \     2        2*n                                                 |      ||                       \             2*n                                           |   ||                                     \     3        2*n                                                         |
    ||                   \   (3 + x)                                              |     ||                              \   n *(3 + x)                                                    |      ||                        \   n*(3 + x)                                              |   ||                                      \   n *(3 + x)                                                            |
    ||                   /   ----------                           otherwise       |     ||                              /   -------------                                   otherwise     |      ||                        /   ------------                             otherwise     |   ||                                      /   -------------                                           otherwise     |
    ||                  /     3 + 2*n                                             |     ||                             /       3 + 2*n                                                    |      ||                       /      3 + 2*n                                              |   ||                                     /       3 + 2*n                                                            |
    ||                 /___,                                                      |     ||                            /___,                                                               |      ||                      /___,                                                        |   ||                                    /___,                                                                       |
    ||                 n = 1                                                      |     \\                            n = 1                                                               /      \\                      n = 1                                                        /   \\                                    n = 1                                                                       /
    \\                                                                            /                                                                                                                                                                                                                                                                                                                          
$$- 8 \left(\begin{cases} \frac{\left(x + 3\right)^{2} \left(\frac{- \frac{5 \left(x + 3\right)^{2}}{3} - 5}{\left(x + 3\right)^{4}} + \frac{5 \operatorname{atanh}{\left(\sqrt{\left(x + 3\right)^{2}} \right)}}{\left(x + 3\right)^{4} \sqrt{\left(x + 3\right)^{2}}}\right)}{5} & \text{for}\: x > -4 \wedge x < -2 \\\sum_{n=1}^{\infty} \frac{\left(x + 3\right)^{2 n}}{2 n + 3} & \text{otherwise} \end{cases}\right) + 12 \left(\begin{cases} \frac{\left(x + 3\right)^{2} \left(\frac{10 \left(x + 3\right)^{2} - 15}{2 \left(x + 3\right)^{6} - 2 \left(x + 3\right)^{4}} - \frac{15 \operatorname{atanh}{\left(\sqrt{\left(x + 3\right)^{2}} \right)}}{2 \left(x + 3\right)^{4} \sqrt{\left(x + 3\right)^{2}}}\right)}{5} & \text{for}\: \left|{\left(x + 3\right)^{2}}\right| < 1 \\\sum_{n=1}^{\infty} \frac{n \left(x + 3\right)^{2 n}}{2 n + 3} & \text{otherwise} \end{cases}\right) - 6 \left(\begin{cases} \frac{\left(x + 3\right)^{2} \left(\frac{- 20 \left(x + 3\right)^{4} + 75 \left(x + 3\right)^{2} - 45}{4 \left(x + 3\right)^{8} - 8 \left(x + 3\right)^{6} + 4 \left(x + 3\right)^{4}} + \frac{45 \operatorname{atanh}{\left(\sqrt{\left(x + 3\right)^{2}} \right)}}{4 \left(x + 3\right)^{4} \sqrt{\left(x + 3\right)^{2}}}\right)}{5} & \text{for}\: \left|{\left(x + 3\right)^{2}}\right| < 1 \\\sum_{n=1}^{\infty} \frac{n^{2} \left(x + 3\right)^{2 n}}{2 n + 3} & \text{otherwise} \end{cases}\right) + \begin{cases} \frac{\left(x + 3\right)^{2} \left(\frac{40 \left(x + 3\right)^{6} - 305 \left(x + 3\right)^{4} + 360 \left(x + 3\right)^{2} - 135}{8 \left(x + 3\right)^{10} - 24 \left(x + 3\right)^{8} + 24 \left(x + 3\right)^{6} - 8 \left(x + 3\right)^{4}} - \frac{135 \operatorname{atanh}{\left(\sqrt{\left(x + 3\right)^{2}} \right)}}{8 \left(x + 3\right)^{4} \sqrt{\left(x + 3\right)^{2}}}\right)}{5} & \text{for}\: \left|{\left(x + 3\right)^{2}}\right| < 1 \\\sum_{n=1}^{\infty} \frac{n^{3} \left(x + 3\right)^{2 n}}{2 n + 3} & \text{otherwise} \end{cases}$$
-8*Piecewise(((3 + x)^2*((-5 - 5*(3 + x)^2/3)/(3 + x)^4 + 5*atanh(sqrt((3 + x)^2))/(sqrt((3 + x)^2)*(3 + x)^4))/5, (x > -4)∧(x < -2)), (Sum((3 + x)^(2*n)/(3 + 2*n), (n, 1, oo)), True)) - 6*Piecewise(((3 + x)^2*((-45 - 20*(3 + x)^4 + 75*(3 + x)^2)/(-8*(3 + x)^6 + 4*(3 + x)^4 + 4*(3 + x)^8) + 45*atanh(sqrt((3 + x)^2))/(4*sqrt((3 + x)^2)*(3 + x)^4))/5, Abs((3 + x)^2) < 1), (Sum(n^2*(3 + x)^(2*n)/(3 + 2*n), (n, 1, oo)), True)) + 12*Piecewise(((3 + x)^2*((-15 + 10*(3 + x)^2)/(-2*(3 + x)^4 + 2*(3 + x)^6) - 15*atanh(sqrt((3 + x)^2))/(2*sqrt((3 + x)^2)*(3 + x)^4))/5, Abs((3 + x)^2) < 1), (Sum(n*(3 + x)^(2*n)/(3 + 2*n), (n, 1, oo)), True)) + Piecewise(((3 + x)^2*((-135 - 305*(3 + x)^4 + 40*(3 + x)^6 + 360*(3 + x)^2)/(-24*(3 + x)^8 - 8*(3 + x)^4 + 8*(3 + x)^10 + 24*(3 + x)^6) - 135*atanh(sqrt((3 + x)^2))/(8*sqrt((3 + x)^2)*(3 + x)^4))/5, Abs((3 + x)^2) < 1), (Sum(n^3*(3 + x)^(2*n)/(3 + 2*n), (n, 1, oo)), True))

    Ejemplos de hallazgo de la suma de la serie