1.be helpful in doing sth.
例如We hope this leaflet has been helpful in answering your questions.
我們希望這個宣傳單可以幫助您找到您想要的答案
2.it is helpful (for sb) to do sth
It is helpful to discuss your problems with your friends.
-跟你的朋友們聊聊你遇到的問題是有好處的.這里的It是形式主語,真正的主語是to后面的句子
3.be helpful for sb對某人事有益的
例如;Music with the sounds of the ocean or bird song can be helpful for some.
大海的聲音或者鳥叫聲對你的睡眠時很有幫助的