A:NH 4+ +H2O⇌NH3•H2O+H+
B:Br﹣+H2O⇌HBr+OH﹣
C:CO 32− +2H2O⇌H2CO3+2OH﹣
D:Fe3++3H2O⇌Fe(OH)3↓+3H+
已知反比例函数y=k-3x的图象如图所示,则k的取值范围是( )
①____ "U" ②____ice cream ③____girl ④____ "S"
一列数a1,a2,a3,…,其中a1=12,an=11-an-1(a为不小于2的整数),则a2014=( )
①若数列{an}既是等差数列又是等比数列,则Sn=na1;
②若Sn=2n﹣1,则数列{an}是等比数列;
③若Sn=an2+bn(a,b∈R),则数列{an}是等差数列;
④若Sn=an(a∈R),则数列{an}既是等差数列又是等比数列.
其中正确结论的序号是____.