不定式
1) 不定式常在下面动词后面作宾语：afford, agree, arrange, ask, attempt, beg, care, choose, claim, decide, desire, determine, expect, fail, hope, pretend, promise, refuse, learn, tend, long, manage, offer, plan, prepare, etc.
2) 动词 + it(形式宾语) + 形容词(宾语补足语)+ 不定式(真正宾语)，适用于此结构的动词：believe, consider, feel, find, realize, see, suppose, think, understand etc.
We found it impossible to get everything ready in time.
3) “Wh- word + 不定式” 结构
advise, decide, discuss, find out, know, learn, see, teach, tell, show understand, wonder 等
He does not know when to start.
You can decide whether to continue or to stop.
I will show you how to deal with it.
注意下面两个句子的区别：
I cannot decide which restaurant to go to. / I cannot decide where to go.
不定式作宾语补足语
1) 动词ask, advise, allow, beg, cause, command, direct, enable, encourage, expect, feel, force, have, hear, invite, lead, let, make, notice, order, permit, persuade, tell, urge, watch, see, require etc.
2) 下列词组后面的不定式不带to：would rather … than… (宁愿…也不)，had better ，can’t help but …(不得不), may/might as well … (不妨)
务必注意的是：接不带to的不定式作宾补的动词改成被动形式时必须加to。
He has seen nine presidents come and go.
Nine presidents have been seen to come and go (by him).
He will make you announce the news.
You’ll be made to announce the news.
不定式作状语:表示行为的目的，结果
注意 so as to和in order to的区别
so as to 句中
(in order) to 句首或句中
下列结构表示结果：
enough to …(注意enough的位置),
too … to…,
only to…
I rushed to the station as fast as I could, only to find the train already gone.
不定式的时态
1) 完成式:不定式的动作在谓语表示的动作之前完成,或想像中过去的动作或事情,但并没有发生。
This book is said to have been translated into dozens of languages in the last decade.
The plane was to have taken off at six, but something went wrong.
2) 进行式：
The children appear to be enjoying themselves at the party.
注意不定式的逻辑主语 of sb./for sb.
It is quite important for us to learn a foreign language well.
It is very kind of you to tell me the truth.
判断标准
(1) 看形容词的性质 当作表语的形容词表示人的品质特点时(如： careless, clever, considerate, foolish, good, impolite, kind, naughty, nice, silly, stupid, wise 等)作表语时，逻辑主语用of 引出
(2) 如果能改成 Sb. be +adj.+to do sth. 就用of.