【单选题】What’s the disadvantage of e-mail according to the passage?
A.
It has to many junk mails.
B.
I t has no way to know if the person has read the message immediately .
C.
It assumes that the minute someone receives an e-mail, the person will read it.
【简答题】已知数列{ a n }满足 a 1 =0, a 2 =2,且对任意 m 、 n ∈ N * 都有 a 2 m - 1 + a 2 n - 1 =2 a m + n - 1 +2( m - n ) 2 (Ⅰ)求 a 3 , a 5 ; (Ⅱ)设 b n = a 2 n + 1 - a 2 n - 1 ( n ∈ N * ),证明:{ b n }是等差数列; (Ⅲ)设 c n =( a n+1 - a...
【判断题】连锁企业面对宏观环境因素的态度是改变环境。
【简答题】设数列 的前n项和为 ,已知 , (1)设 ,证明数列 是等比数列 (2)求数列 的前 项和
【单选题】电压比较器电路如图a所示,则当输入电压uI的波形如图b所示时,灯泡HL的亮暗状态为( )【图片】
【判断题】设有两个正规格化数:N 1 =2 m ×M 1 , N 2 =2 n ×M 2 ,若m>n,不一定 N 1 > N 2 。
【单选题】有一单门限电压比较器基本电路如图所示,它的输入输出特性具有 ( )