get down to 与set about to

get down to （静下心来）认真处理 （工作等）,开始认真注意 （细节等）.
e.g.After Christmas I'm going to get down to some serious job-hunting.
圣诞节后,我打算开始认真的找工作.
get down to 里面的to 应该是介词,后面跟动词的ing形式.有点像look foward to 里面的to,都是介词,后面都需要跟动词的ing形式.
get down 后面不跟 to do.
get down 表示渐渐的使某人不快,疲倦
All this waiting and delay is really getting her down.
get sth.down 表示记下,写下（尤指某人说的话）
好像没有set about to do的用法,但是有set about
set about 表示开始,着手做某事,可以说set about doing sth.表示开始（着手）做某事,尤其指费事,费劲的事.
She set about clearing up after the party.
聚会之后,他开始收拾东西打扫卫生.
set out to do 表示为达到某个结果而开始做某事,着手进行计划.
She deliverately set out to poison her husband.
她蓄谋毒杀她的丈夫.
它们之间的区别,你就可以在解释当中明了了.谢谢你。非常感谢。^_^ 只是期待能有一个人来帮助我。That's OK! I hope you can improve your English by using dictionary. All the answers can be looked up in a dictionary. That is easy! :)