Which of these infinite series converges?
∑n=1∞(1.1)n\sum_{n=1}^{\infty} (1.1)^n∑n=1∞(1.1)n
∑n=1∞(−0.9)n\sum_{n=1}^{\infty} (-0.9)^n∑n=1∞(−0.9)n
∑n=1∞2n\sum_{n=1}^{\infty} 2^n∑n=1∞2n
∑n=1∞(π3)n\sum_{n=1}^{\infty} (\frac{\pi}{3})^n∑n=1∞(3π)n