Which of the Following Is a Power Series?
1) $1 + \frac { 3 } { x } + 3 x ^ { 4 }$

Multiple Choice

Which of the following is a power series?
1) $1 + \frac { 3 } { x } + 3 x ^ { 4 }$
2) $\sum _ { n = 1 } ^ { \infty } 3 ^ { n } x ^ { - n }$
3) $\sum _ { n = 1 } ^ { \infty } ( - 1 ) ^ { n - 1 } ( 2 x + 1 ) ^ { n }$

A) None
B) 1
C) 2
D) 3
E) 1, 2
F) 1, 3
G) 2, 3
H) 1, 2, 3