若命题p:∀x∈R,x2-1>0,则命题p的否定是 ______.
∵命题p:∀x∈R,x2-1>0,
命题p的否定是∃x∈R,x2-1≤0
故答案为:∃x∈R,x2-1≤0
“Well done, John.! Not a single mistake _____ in your exam paper this time!”said the teacher.
A.you made
B.did you make
C.had you made
D.you have made
制发档案证明应注意的问题?