you'd better do sth 你最好做某事 否定是you'd better not do sth.而you'd better don't do sth是錯誤的.就像tell sb to do sth的否定是tell sb not do sth,不能寫成tell sb don't to do sth.那can呢？ you can't do sth。是你不可以做某事，那 你可以不做某事，是不是可以說 you can don‘t do sth？那也是不對的。can的否定形式便是can not或者縮略形式can't. 表示不能夠做某事。你可以不做某事，我們可以翻譯成you need not to do that thing. 你不必做那件事的。