What is the derivative of the series ∑n=1∞xnn\sum_{n=1}^{\infty} \frac{x^n}{n}∑n=1∞nxn?
∑n=0∞xn\sum_{n=0}^{\infty} x^n∑n=0∞xn
∑n=1∞xn−1\sum_{n=1}^{\infty} x^{n-1}∑n=1∞xn−1
∑n=1∞nxn−1\sum_{n=1}^{\infty} n x^{n-1}∑n=1∞nxn−1
11−x\frac{1}{1-x}1−x1