陆旭老师，我有一些做过的assumption题目取非的句子搞不清，你能帮忙看下吗(不说这道题目的解题思路，单纯就是取非问题，特别是双重否定或者从句里面有否定词） 1.No part of a person’s brain that is damaged by a stroke ever recovers.---> some part of a person's brain that is damaged by a stroke ever recovers. 2.Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.这个句子我不太会取非，正过来说这个句子就是Impairment of linguistic capabilities occurs in people who have suffered any damage to any language center of the brain.那么我取非是Impairment of linguistic capabilities occurs in people who have not suffered any damage to any language center of the brain. 3.If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them. 取非If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages nothing of them. 4.这题出现两个not The collection fee will not significantly affect the purchasing power of most residents, even if their households do not reduce the amount of trash they put out. 我取非直接去前面的not: The collection fee will significantly affect the purchasing power of most residents, even if their households do not reduce the amount of trash they put out. 5.这个也差不多 Not all steel producers were unaffected by country A’s newly imposed tariffs. 我取非All steel producers were unaffected bycountry A’s newly imposed tariffs. 6.There are no plants native to western Africa that, if domesticated, could serve as staple food crops. 这个if domesticated是不是可以不管，直接改成There are some plants native to western Africa that, if domesticated, could serve as staple food crops.

请问这一题的解题思路

求问解题思路

求问解题思路

条件一：（30+⏹）（20+🔼）=864化简为20🔼-🔼^2=64 然后从2开始带入，得出当🔼=4时成立。条件二：⏹✖️🔼=24得出3、8和4、6两组可能解，分别带入，只有36和24成立，所以条件二充分。请问以上这个解题思路对吗，或者说有更简便的？

第14题 请徐老师解答 谢谢！

请问这道题的解题思路

第13题: 听老师jj课里讲的说选C，我不太明白条件2的分析，老师上课说条件2，若st同号，上式取等号，若st一正一负时，上式是小于号。那不就可以通过条件2直接判断上式大于号不成立吗，也就是答案是No。请老师更正下我的思路。

请徐老师讲下这两道题：这两个都做对了 但是感觉做的时候不太自信，想了一会，想听下老师的思路。谢谢老师！

麻烦徐老师讲一下Q9，选了E。我的思路是分析rounding后estimate的最大和最小的差值。

请徐老师讲一下Q7思路。读题是不是很明白题意说的到head的概率不是1/2。