A:①②③④
B:⑤⑥⑦⑧
C:③⑤⑥⑦⑧
D:③④⑤⑥⑦⑧
Today he has much ____ (homework) to do.
已知{an}是等比数列,前n项和为Sn(n∈N*),且 1a1 ﹣ 1a2 = 2a3 ,S6=63.