![](https://static.youtibao.com/asksite/comm/h5/images/m_q_title.png)
[主观题]
等比数列{an}中,若a1 + a2 =30,a3 + a4 =120,则a5 + a6 =() (A)240 (B)480 (C)720 (D)960
等比数列{an}中,若a1 + a2 =30,a3 + a4 =120,则a5 + a6 =() (A)240 (B)480 (C)720 (D)960
查看答案
![](https://static.youtibao.com/asksite/comm/h5/images/solist_ts.png)
等比数列{an}中,若a1 + a2 =30,a3 + a4 =120,则a5 + a6 =() (A)240 (B)480 (C)720 (D)960
已知等差数列的公差d≠0,a1=1/2,且a1,a2,a5成等比数列.
(I)求{an}的通项公式;
(Ⅱ)若{an}的前n项和Sn=50,求n
请帮忙给出每个问题的正确答案和分析,谢谢!
A.=2*$A$1
B.=2*$A1
C.=2*A$1
D.=2*Al
已知{an},{bn}分别为等比数列与等差数列,a1=b1=1,则b2≥a2.
(1)a2>0
(2)a10=b10E.
已知{an},{bn}分别为等比数列与等差数列,a1=b1=1,则b2≥a2.
(1)a2>0
(2)a10=b10E.
A.=2$A$1
B.=2$A1
C.=2+$A$1
D.=2+A1
A.=2*SA$1
B.=2*$A1
C.=2*A$1
D.=2*A1