【简答题】若函数 在 上可导, ,则 ______;
【单选题】如果f(χ)在χ0可导,g(χ)在χ0不可导,则f(χ)g(χ)在χ0:
【简答题】已知a、b、m、n∈N + ,{a n }是首项为a,公差为b的等差数列;{b n }是首项为b,公比为a的等比数列,且满足a 1 <b 1 <a 2 <b 2 <a 3 . (1)求a的值; (2)数列{1+a m }与数列{b n }的公共项,且公共项按原顺序排列后构成一个新数列{c n },求{c n }的前n项之和S n .
【单选题】It is getting diff icult 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 f ierce
【简答题】如图所示的n×n的数表,满足每一行都是公差为d的等差数列,每一列都是公比为q的等比数列.已知a 11 =a,则a 11 +a 22 +…+a nn =______. . a 11 a 12 … a 1n a 21 a 22 … a 2n ? ? … ? ? ? … ? ? ? … ? a n1 a n2 … a nn . .