很简单啊.
举个最简单的例子
You can find the answer.(转换为否定句)
=You can't find the answer.
(转换为一般疑问句)
=Can you find the answer?
(否定疑问句)
=Can't you find the answer?
其实就是将句子中be动词/动词转化为否定形式.
或者添加否定词语.例如:You can never find the answer.