问题
解答题
写出命题“若a＞0且b＞0，则ab＞0．”的逆命题、否命题、逆否命题．并判断它们的真假．
答案
解析：原命题的逆命题：若ab＞0．则a＞0且b＞0，假命题．…4分
原命题的否命题：若a≤0或b≤0．则ab≤0．假命题 …9分
原命题的逆否命题：若ab≤0．则a≤0或b≤0．真命题…12分．
搜题请搜索小程序“爱下问搜题”
写出命题“若a＞0且b＞0，则ab＞0．”的逆命题、否命题、逆否命题．并判断它们的真假．
解析：原命题的逆命题：若ab＞0．则a＞0且b＞0，假命题．…4分
原命题的否命题：若a≤0或b≤0．则ab≤0．假命题 …9分
原命题的逆否命题：若ab≤0．则a≤0或b≤0．真命题…12分．
| 短文改错。 | |
| Last night when Jim was going over his lesson,his grandma came into her room and chatted with him for a while.Then she got up from the sofa and wanted go to her bedroom. And suddenly she fell down to the ground.Jim was very frightened.Knew her heart trouble must have come again, he quickly phoned nearest hospital for help.Before the doctors came,he helped his grandma lay on her back and comfort her,which made her feel better.Soon help came in and his grandma was sent to hospital at once.One doctor said Jim has done the right thing and actually saved her life | 1._________ 2._________ 3._________ 4._________ 5._________ 6._________ 7._________ 8._________ 9._________ 10.________ |