幂级数的收敛域为（）。
参考答案：[-A,A)
解析：
—Congratulations! Among the best pictures in the competition，I found _______. Why did you draw it?
一During the trip to the Yellow Mountain _______ May.
A．yours; in
B．yours; on
C．you; in
D．you; on
-- ________ your homework yet?
-- Not yet. I _______ it.
A．Have you done; am doing
B．Did you do; am doing
C．Have you done; did
D．Did you do; did
的收敛域为（）。
的收敛域为（）。