What is the interval of convergence for ∑n=1∞xnnn\sum_{n=1}^{\infty} \frac{x^n}{n^n}∑n=1∞nnxn?
(−1,1)(-1, 1)(−1,1)
[−1,1][-1, 1][−1,1]
(−∞,∞)(-\infty, \infty)(−∞,∞)
(0,1)(0, 1)(0,1)