A.命题“若x2-5x+6=0,则x=2”的逆否命题是“若x≠2,则x2-5x+6≠0” | ||
B.若x,y∈R,则“x=y”是xy≥(
| ||
C.已知命题p和q,若p∨q为假命题,则命题p与q必一真一假 | ||
D.对命题p:∃x∈R,使得x2+x+1<0,则¬p:∀x∈R,则x2+x+1≥0 |
x+y |
2 |
x+y |
2 |
π |
3 |
A.-a≤a≤1 | B.a≤-2或1≤a≤2 |
C.a≥1 | D.a=1或a≤-2 |
2 |
A.¬p是假命题 | B.¬q是真命题 |
C.p∨q是真命题 | D.¬p∧¬q是真命题 |
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