在等比数列{an}中,已知q=2,S4=1,求S8
人气：357 ℃ 时间：2020-09-19 07:24:00
解答
s8=a1(1-q^8)/(1-q)
=a1(1-q^4)(1+q^4)/(1-q)
=(1+q^4)*[a1(1-q^4)/(1-q)]
=(1+q^4)*S4
=(1+2^4)*1
=1+16
=17
推荐
- 等比数列an.q＝2.S4＝1,求S8
- 等比数列an,q小于0,S4＝1,S8=17,求q
- 在等比数列｛an｝中,（1）已知q=2,S4=1,求S8（2）a3=-12,S3=-9,求公比q
- an为等比数列,q=2,前4项和S4=1,则前8项和S8的值为
- 设等比数列{an}的前n项和为Sn，S4=1，S8=17，求通项公式an．
- 鱼虱子为什么能浮在水面上?请用物理知识回答.
- 味觉和嗅觉感受器均感受什么信息,两者相互影响形成味觉
- After having been wounded towards the end of the war,he had been sent to hospital and was separated from his unit.
猜你喜欢
