請問Could we...和Couldn't we....有什麼分別?

Could we是正常的問題，發問者心裏並沒有帶著答案，如：
Could we dine together tonight?（我們今晚一起用膳？）
發問者心裏並不期望你一定要答yes or no
但couldn't we這類問題，是rhetorical question，發問者心裏是期望你答：yes, we can.
如：Couldn't we do that?（我們不可做這事嗎？）（發問者，期望答案是：當然可以）
但若你不行，你照樣可以答：No, we can't

希望幫到你！

could we.....

詢問

Could we drive your car to school ??


couldn't we.....

提議

Couldn't we take a taxi instead of bus ??