I have a problem with series $\sum_{k=1}^ \infty k*(\frac{1}{2})^{k+2}$ How can I solve it?
Asked
Active
Viewed 20 times
0
-
1Try talking to her – Jan 22 '17 at 17:10
-
Consistent 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 $$\frac 14\sum_{k=1}^\infty k\left(\frac 12\right)^k$$ – amWhy Jan 22 '17 at 17:17
-
@Winther thanks! – Anne Jan 22 '17 at 17:23