do a person a favor
= do a favor for a person答应某人的请求,帮某人的忙,给予某人恩惠
Will you do me a favor? 你愿意帮我忙吗?
do a person good
对 <人 (的身体) > 有益
Smoking won't do you any good. 吸烟对你的身体无益
It will do you more harm than good. 它对你的害处多于益处; 它对你有害无益
Much good may it do you !. (反语)但愿它对你大有用处(它对你没什么用处)
