I have a problem with series $\sum_{k=1}^ \infty k*(\frac{1}{2})^{k+2}$ How can I solve it?
problem with a series
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analysis
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1Try talking to her – 2017-01-22
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0Consistent with the duplicate @Winther found, note that $$k\left(\frac 12\right)^{k+2} = \left(\frac 12\right)^2 \cdot k\cdot \left(\frac 12\right)^k$$ In other words, you have the sum $$\frac 14\sum_{k=1}^\infty k\left(\frac 12\right)^k$$ – 2017-01-22
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0@Winther thanks! – 2017-01-22