题目内容
x∈R,x2+1≥0
①命题“所有的四边形都是矩形”是特称命题
②命题“x∈R,x2+1＜0”是全称命题
③若p: x∈R,x2+2x+1≤0,则p: x∈R,x2+2x+1≤0
A.0 B.1 C.2 D.3
（2）命题“x∈R,x2+1＜0”的否定是 .
(2)命题“x∈R,x2+1＜0”的否定是_______.
x∈R,x2+1＜0的否定是___________.x∈R,x2+1≥0
x∈R,x2+1＜0的否定是___________.x∈R,x2+1＜0的否定是___________.x∈R,x2+1≥0
x∈R,x2+1＜0”是全称命题 
x∈R,x2+2x+1≤0,则
p: 
x∈R,x2+2x+1≤0
x∈R,x2-x+3＞
x∈R,x2+1＜
x∈R,x2-x+3＞0”的否定是_______.
x∈R,x2+1＜0”的否定是_______.
x∈R，x2-x+3＞0的否定是________，命题
x∈R,x2+1＜0的否定是________.