1. You might as well reason with him as reason with a wolf. （误）

2. You may as well expect a river to flow backward as expect him to change his mind. （正）

网友看问题还是很尖锐的。

1. 《当代高级英语语法》里的这两个英语句子，第一个是错的，意思跟汉语恰恰相反。第二个正确。不知作者是怎么理解的，一样的结构，却把意思理解反了。

2. may/might as well 这是很常见，很常用的一个表达。用来表示建议、忠告，意思是：“最好还是；还不如”。

You may as well stay here. 你最好还是呆在这儿。 =  你还不如呆在这儿。

3. 以上两个比喻，是借助于 may/might as well 中的 as，构成“比较句”：as...as...

在比较分句中，为了简练，承前省略了相同的主语“you”。

4. 句 1 错误，改为：

You might as well reason with a wolf as （you ）reason with him.

句子不难理解，按字面翻译即可：

“比起跟他讲道理，你还不如跟豺狼讲道理。”

句 2 按字面翻译也很好懂：

You may as well expect a river to flow backward as expect him to change his mind.

“比起指望他改变主意，你还不如指望河水倒流。” 

原翻译只是拐了一个弯，其实，意思没有区别。

【注】第二句，网友是不是抄错了句子：expect him to change my mind. 你不能使我改变主意——人称有点乱，需要统一。