why not与what about与why don‘t you与how about与why not you的区别

Why not +动词原形...=Why don't you +动词原形...
=What about doing ...=How about doing ...
这几个没有区别,可以换用.都是征求对方意见的,"...怎么样?"
没有why not you的说法.
例:How/What about going for a walk
= Why not go for a walk
=Why don't you go for a walk
再问： shall we +动词原型？
再答： shall we +动词原型？用来征求对方意见也可以. Shall we go for a walk ? 我们去散步好吗? =How/What about going for a walk ? 你认为我们去散步怎么样?