肯定句变否定句的基本方法：动词be根据不同的人称和时态可以有am, is, are, was, were等不同形式，可用作连系动词(表示“是”、“在”等)和助动词(用于构成进行时态和被动语态等)，但不管何种情况，构成否定式时，一律在其后加not。
例如I’m old, but you’re young. 我老了，但你还年轻。改I’m not old, but you’re not young. 我还不老，但你不年轻了。
扩展资料：
一般否定句：
I don't know this. No news is good news.
There is no person（smoking）/not a person/not any person（smoking）in the house.
特指否定：
He went to his office, not to see him.
I am sorry for not coming on time.
I don't think / believe/suppose / feel / imagine you are right.
参考资料来源：百度百科-否定句
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