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



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Solución

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

    Ejemplos de hallazgo de la suma de la serie