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Sum of series -1(1-q^n)



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The solution

You have entered [src]
  oo           
 ___           
 \  `          
  \    /     n\
  /   -\1 - q /
 /__,          
n = 1          
$$\sum_{n=1}^{\infty} - (1 - q^{n})$$
Sum(-(1 - q^n), (n, 1, oo))
The answer [src]
      //   q                 \
      || -----    for |q| < 1|
      || 1 - q               |
      ||                     |
      ||  oo                 |
-oo + |< ___                 |
      || \  `                |
      ||  \    n             |
      ||  /   q    otherwise |
      || /__,                |
      \\n = 1                /
$$\begin{cases} \frac{q}{1 - q} & \text{for}\: \left|{q}\right| < 1 \\\sum_{n=1}^{\infty} q^{n} & \text{otherwise} \end{cases} - \infty$$
-oo + Piecewise((q/(1 - q), |q| < 1), (Sum(q^n, (n, 1, oo)), True))

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