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Suma de la serie (1+(-1)^n)*(x^(3n+5))/(3n+1)



=

Solución

Ha introducido [src]
  oo                      
____                      
\   `                     
 \    /        n\  3*n + 5
  \   \1 + (-1) /*x       
  /   --------------------
 /          3*n + 1       
/___,                     
n = 1                     
$$\sum_{n=1}^{\infty} \frac{x^{3 n + 5} \left(\left(-1\right)^{n} + 1\right)}{3 n + 1}$$
Sum(((1 + (-1)^n)*x^(3*n + 5))/(3*n + 1), (n, 1, oo))
Respuesta [src]
   //    /                             -pi*I     /       pi*I\      pi*I    /       5*pi*I\\                          \      //   /                           -2*pi*I    /       2*pi*I\      2*pi*I    /       4*pi*I\\                         \
   ||    |                             ------    |       ----|      ----    |       ------||                          |      ||   |                           -------    |       ------|      ------    |       ------||                         |
   ||    |          /       pi*I\        3       |        3  |       3      |         3   ||                          |      ||   |                              3       |         3   |        3       |         3   ||                         |
   ||    |     4*log\1 - x*e    /   4*e      *log\1 - x*e    /   4*e    *log\1 - x*e      /|                          |      ||   |         4*log(1 - x)   4*e       *log\1 - x*e      /   4*e      *log\1 - x*e      /|                         |
   ||    |     ------------------ - -------------------------- - --------------------------|                          |      ||   |       - ------------ - ----------------------------- - ----------------------------|                         |
   ||  3 |4           3*x                      3*x                          3*x            |                          |      || 3 |  4          3*x                     3*x                            3*x             |                         |
   ||-x *|-- - ----------------------------------------------------------------------------|                          |      ||x *|- -- + -----------------------------------------------------------------------------|                         |
   ||    | 3                                         3                                     |                          |      ||   |   3                                          3                                     |                         |
   ||    \x                                         x                                      /                          |      ||   \  x                                          x                                      /                         |
 5 ||----------------------------------------------------------------------------------------  for And(x <= 1, x > -1)|    5 ||-----------------------------------------------------------------------------------------  for And(x >= -1, x < 1)|
x *|<                                           4                                                                     | + x *|<                                            4                                                                     |
   ||                                                                                                                 |      ||                                                                                                                  |
   ||                                      oo                                                                         |      ||                                        oo                                                                        |
   ||                                    ____                                                                         |      ||                                      ____                                                                        |
   ||                                    \   `                                                                        |      ||                                      \   `                                                                       |
   ||                                     \        n  3*n                                                             |      ||                                       \       3*n                                                                |
   ||                                      \   (-1) *x                                                                |      ||                                        \     x                                                                   |
   ||                                      /   ----------                                             otherwise       |      ||                                        /   -------                                               otherwise       |
   ||                                     /     1 + 3*n                                                               |      ||                                       /    1 + 3*n                                                               |
   ||                                    /___,                                                                        |      ||                                      /___,                                                                       |
   \\                                    n = 1                                                                        /      \\                                      n = 1                                                                       /
$$x^{5} \left(\begin{cases} \frac{x^{3} \left(\frac{- \frac{4 \log{\left(1 - x \right)}}{3 x} - \frac{4 e^{- \frac{2 i \pi}{3}} \log{\left(- x e^{\frac{2 i \pi}{3}} + 1 \right)}}{3 x} - \frac{4 e^{\frac{2 i \pi}{3}} \log{\left(- x e^{\frac{4 i \pi}{3}} + 1 \right)}}{3 x}}{x^{3}} - \frac{4}{x^{3}}\right)}{4} & \text{for}\: x \geq -1 \wedge x < 1 \\\sum_{n=1}^{\infty} \frac{x^{3 n}}{3 n + 1} & \text{otherwise} \end{cases}\right) + x^{5} \left(\begin{cases} - \frac{x^{3} \left(- \frac{- \frac{4 e^{- \frac{i \pi}{3}} \log{\left(- x e^{\frac{i \pi}{3}} + 1 \right)}}{3 x} + \frac{4 \log{\left(- x e^{i \pi} + 1 \right)}}{3 x} - \frac{4 e^{\frac{i \pi}{3}} \log{\left(- x e^{\frac{5 i \pi}{3}} + 1 \right)}}{3 x}}{x^{3}} + \frac{4}{x^{3}}\right)}{4} & \text{for}\: x \leq 1 \wedge x > -1 \\\sum_{n=1}^{\infty} \frac{\left(-1\right)^{n} x^{3 n}}{3 n + 1} & \text{otherwise} \end{cases}\right)$$
x^5*Piecewise((-x^3*(4/x^3 - (4*log(1 - x*exp_polar(pi*i))/(3*x) - 4*exp(-pi*i/3)*log(1 - x*exp_polar(pi*i/3))/(3*x) - 4*exp(pi*i/3)*log(1 - x*exp_polar(5*pi*i/3))/(3*x))/x^3)/4, (x <= 1)∧(x > -1)), (Sum((-1)^n*x^(3*n)/(1 + 3*n), (n, 1, oo)), True)) + x^5*Piecewise((x^3*(-4/x^3 + (-4*log(1 - x)/(3*x) - 4*exp(-2*pi*i/3)*log(1 - x*exp_polar(2*pi*i/3))/(3*x) - 4*exp(2*pi*i/3)*log(1 - x*exp_polar(4*pi*i/3))/(3*x))/x^3)/4, (x >= -1)∧(x < 1)), (Sum(x^(3*n)/(1 + 3*n), (n, 1, oo)), True))

    Ejemplos de hallazgo de la suma de la serie