The power series ∑n=0∞(−1)nxn\sum_{n=0}^{\infty} (-1)^n x^n∑n=0∞(−1)nxn converges to which function?
11+x\frac{1}{1+x}1+x1 for ∣x∣<1|x| < 1∣x∣<1
11−x\frac{1}{1-x}1−x1 for ∣x∣<1|x| < 1∣x∣<1
e−xe^{-x}e−x for all xxx
cos(x)\cos(x)cos(x) for all xxx