上期我们研究了一般过去时的定义，构成，和常用的时间状语，本期我们研究一般过去时当中，陈述句变为否定句、疑问句以及肯定答语和否定答语等。

(一）陈述句变为否定句：1、如果句子中是be 动词(was /were )、情态动词(could ,might 等)只需在它们后面加not 即可。

I was a student. →I was not /wasn't a student.

It was a train. →It was not /wasn't a train.

They were workers. →They were not /weren't workers.

He could swim at the age of 6.

六岁时他能游泳。

→He could not / couldn't swim at the age of 6.

2、如果句子中是实义动词，需要借助助动词(did )来构成否定句。在一般过去时中，句子谓语动词是实义动词时，只需用did 即可，不需要考虑人称、数等因素。

(1） I worked here last year.

→I did not /didn't work here last year.

(2) He went to Beijing last month.

→ He did not /didn't go to Beijing last month.

(3）Tom did his homework at home.

→He didn't do his homework at home.

精析：第三个例子，特别要注意，这里did (做)是实义动词，不能把它认为是助动词did, 而在它后直接加not。大家要知道，助动词不能单独作谓语。还需要借助助动词did 来构成否定句。

重点提示：(1)用了助动词，后面的动 词一律用原形。

(2)变否定句时，如果你记 不 清缩写的形式，直接 用be 动词、情态动词和 助动词后加not 形式。

本期我们主要研究了一般过去时陈述句变否定句的情况，下期我们研究变疑问句语法规则，欢迎大家点赞评论，关注转发互动交流。Thank you, everybody! Bye, See you next time!