- #1
toothpaste666
- 516
- 20
Homework Statement
find the sum of the following series:
[itex] \sum_{n=1}^\infty nx^{n-1} , |x|<1 [/itex]
Homework Equations
[itex] \frac{a}{1-r} [/itex]
The Attempt at a Solution
i know that a function representation for that series is [itex] -\frac{1}{(1-x)^2} [/itex] but how is it possible to find the sum of a series with a variable in it? please help :(
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