等比数列{an}的各项均为正数,且2a1+3a2=1,a32=9a2a6(Ⅰ)求 发布时间:2017-05-01 18:10 │ 来源:www.tikuol.com 题型:解答题 问题: 等比数列{an}的各项均为正数,且2a1+3a2=1,a32=9a2a6(Ⅰ)求数列{an}的通项公式.(Ⅱ)设bn=1an,求数列{bn}的前n项和.
题型:解答题 选择补全对话。A: Look! 1_______ the boy? A: 3_______ is he doing? A: Does he 4_______ that jacket? A: 5_______ 6_______ pairs of socks 7_______ he have? A: Does he need 8_______ shirts 9_______?B: 2_______ is Li Ming. B: He is packing his suit case. B: No, he doesn't. B: He has one pair of socks. B: Yes, he 10_______. ( ) 1. A. who's( ) 2. A. He ( ) 3. A. Where( ) 4. A. want ( ) 5. A. How ( ) 6. A. many ( ) 7. A. do ( ) 8. A. a ( ) 9. A. two ( ) 10. A. do B. whoseB. He's B. What B. wantsB. What B. much B. is B. much B. to B. does C. whose's C. His C. How C. wanting C. Where C. old C. can C. an C. too C. is D. what's D. He D. When D. to wantD. Who D. tall D. does D. more D. either D. can 查看答案
题型:解答题 [物理选修3—4](本题共有二小题,第一小题5分,第二小题10分,共15分)(1)一列简谐横波沿x轴传播.t =0时的波形如图所示,质点A与质点B相距lm,A点速度沿y轴正方向;t=0.02s时,质点A第一次到达正向最大位移处.由此可知 A.此波的传播速度为25m/sB.此波沿x轴负方向传播 C.从t=0时起,经过0.04s,质点A沿波传播方向迁移了1mD.在t=0.04s时,质点B处在平衡位置,速度沿y轴负方向(2)如图所示,透明介质球球心位于O,半径为R,光线DC平行于直径AOB射到介质的C点,DC与AB的距离H=R/2,若DC光线进入介质球后经一次反射再次回到介质球的界面时,从球内折射出的光线与入射光线平行,作出光路图,并算出介质的折射率。 查看答案
题型:解答题 设NA表示阿伏加德罗常数,下列叙述中不正确的是( )A.通常状况下,1mol SO3含有的分子数为NA个B.1mol OH一参与电解,提供的电子数目为NA个C.标准状况下,含NA个氩原子的氩气体积约为22.4LD.标准状况下,VL水含有的氧原子个数约为NA 查看答案