若a＞2b＞0，则下列不等式：①
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①∵a＞2b＞0，∴a-2b＞0，b＞0．∴
＜1 a-2b
⇔b＜a-2b，即a＞3b，不一定成立；1 b
②∵a＞2b＞0，∴a-b＞b＞0，∴
＞a-b b(a-b)
，化为b b(a-b)
＞1 b
，因此②成立；1 a-b
③∵a＞2b＞0，∴a-2b＞0，b＞0，但是可能a-2b＞b＞0，或b＞a-2b＞0，或a-2b=b＞0，因此③不一定成立；
④∵②正确，∴④一定不正确．
综上可知：只有②正确．
故答案为②．
| 根据对话内容，从方框内五个选项中，选出能填入空白处的最佳选项 | |
B:I’m looking for a present for my friend, Dave. A:Oh just a moment. There are some toys over there . _ 2 _. Do you like them? B:Yes. I think they are really beautiful. But I want to buy some books. _3_. A:Please come here.There are some picture books and story books. They are very interesting. B:_4__ A:They’re 20 yuan. B:__5__. 1 2 3 4 5 |