【简答题】若 在 上可导, ,则 ____________.
【简答题】已知S n 是公差为d≠0的等差数列{a n }的前n项和,{b n }是公比为1-d的等比数列,若b 1 =a 1 ,b 2 =a 1 a 2 ,b 3 =a 2 a 3 ,则 lim n→∞ S n a 2n =______.
【单选题】已知{a n }是公差为 1 的等差数列, S n 为{a n }的前 n 项和。若 =4 ,则 a 10 =( )
【单选题】It is getting diff cult to disconnect people from their work completely, because .
A.
phones apps and constant connectivity connect people to work all the time
B.
it has become a way of life
C.
competition in the workplace is getting fierce
D.
people want to get promotion and increase their salary
【单选题】已知数列{a n }满足2a n+1 -a n =0(n∈N * ),则数列{a n }一定是( )
【简答题】已知{a n }是公差为2的等差数列,且a 3 +1是a l +1与a 7 +1的等比中项. (1)求数列{a n }的通项公式; (2)令b n = a n -1 2 n (n∈ N * ) ,求数列{b}的前n项和T n .
【单选题】周女士,45岁,近2年来发现外阴左侧有一肿块,疼痛,2个月前破溃,且有血性分泌物,住院诊断为外阴癌,行手术治疗,术后留置导尿管。护士为其进行会阴部擦洗时错误的是