问题
选择题
命题“∀x∈R,x2+1≥1”的否定是( )
A.∀x∈R,x2+1<1
B.∃x∈R,x2+1≤1
C.∃x∈R,x2+1<1
D.∃x∈R,x2+1≥1
答案
∵原命题“∀x∈R,有x2+1≥1”
∴命题“∀x∈R,有x2+1≥1”的否定是:
∃x∈R,使x2+1<1.
故选C.
命题“∀x∈R,x2+1≥1”的否定是( )
A.∀x∈R,x2+1<1
B.∃x∈R,x2+1≤1
C.∃x∈R,x2+1<1
D.∃x∈R,x2+1≥1
∵原命题“∀x∈R,有x2+1≥1”
∴命题“∀x∈R,有x2+1≥1”的否定是:
∃x∈R,使x2+1<1.
故选C.