Sr Examen

Otras calculadoras

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



=

Solución

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