一、解析
首先否定句是 My mother isn't / is not tall and thin. 句意:我的妈妈既不高也不瘦。 然后这句话里面有be 动词 is,所以在be 动词后面加入 not即可, 然后这句话虽然否定句,但是含有两个否定词的句子被看作是肯定句结构,因此用and。
即否定句是 My mother is not tall and thin 或者缩写is not 即My mother isn't tall and thin .(我妈妈既不高也不瘦) 。
二、拓展——变句思路
(1)有 be ,be后面加 not
例一: He is my uncle .(他是我的叔叔)
这句话里面有be 动词 is,否定句在 be 动词 is 后面加not,is not 可以完整写,也可以缩写为 isn't
即 否定句:He is not / isn't my uncle .(他不是我的叔叔。)
(2) 有 can,can后面加 not
例二: She can dance .(她会跳舞,)
这句话里面有情态动词 can,所以否定句在can 后面加 not ,can not 可以完整写,也可以缩写为 can't
即 否定句:She can not / can't dance .(她不会跳舞。)
(3)无 be 无 can找实意动词,前面加don't 或 doesn't,此时动词需要还原
例三: She wants to go to the park .(她想要去公园。)
这句话 dances判断句子一般现在时,并且第三人称单数,所以实意动词 wants 前面加入找动词 doesn’t ,动词还原为want
即 She doesn't want to go to the park.
三、拓展训练
最后来两个小练习巩固一下肯定句变否定句的知识点。
⒈ She likes playing football .
否定句: She does not / doesn't like playing football .
⒉ Nancy wants a football.
否定句: Nancy does not / doesn't want a football.
以上就是这道题的解答以及关于陈述句改为否定句的相关知识点,感谢您的提问,希望可以帮到你,如有帮助请采纳哟!