Which of these infinite geometric series converges?
1+2+4+8+…1 + 2 + 4 + 8 + \dots1+2+4+8+…
10−5+2.5−1.25+…10 - 5 + 2.5 - 1.25 + \dots10−5+2.5−1.25+…
3+3+3+3+…3 + 3 + 3 + 3 + \dots3+3+3+3+…
1+1.1+1.21+1.331+…1 + 1.1 + 1.21 + 1.331 + \dots1+1.1+1.21+1.331+…