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How to calculate infinite series?

  1. Nov 17, 2011 #1
    Hi, I'm stuck on a problem because I don't know how to calculate this series:
    Ʃ(2^n * x^n), n starts from 0 to infinity. How can I calculate this? Do I have to transform it into something else where I know the outcome of the Σ like we do with the geometric functions?
  2. jcsd
  3. Nov 17, 2011 #2
    Let X=2x
    Ʃ(X^n) is the classical geometric series.
  4. Nov 18, 2011 #3
    Thanks, didn't think of doing this.
  5. Nov 18, 2011 #4
    Be advised that |X| < 1 to treat this as a geometric series.
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