We'd better buy an umbrella.(改为否定疑问句）
问题描述：
We'd better buy an umbrella.(改为否定疑问句）
（ ）we ( )buy an umbrella?
答
hadn't we better buy an umbrella?had sb.better do sth.是sb.had better do sth.的疑问形式,had better 的否定形式是加not,所以结合起来我认为就是这样的