形式宾语是什么玩意？

大意我明白，应该跟那个形式主语的作用差不多，希望有人给我有形式宾语的几个句子

形式宾语it常出现在think, feel, believe, expect, consider, find, make 等动词后，如：
Do you think it important to do such a thing?
I believe it no use to do such a thing.
Reading made it possible to practise your English.
例句似乎也可以用形式主语，如：Do you think it is important to do such a thing?但是上述动词后一般只用复合宾语（形式宾语 + 宾补 + 主语）表示而不用形式主语。

形式宾语 1. 若是Vt+名词(O)+形容词(OC)，则不可用形式宾语(it)，例如： He made his intention clear. I will keep myself warm in the heavy clothing. They held her story true after hearing it. Fast transportation has made the round trip possible. 2. 但宾语是不定词或名词子句时，须用形式宾语(it)，写成Vt+it (虚O)+形容词(OC)+ 不定词或名词子句(真O)，例如： He made it clear what he intended to do. I take it for granted that you will give me a hand. They feel it necessary to work harder. Airplanes make it possible to travel around the world in a short time. 3. 前例2全部it (虚O)不能省略。为何用虚宾语(it)呢？因为真宾语太长，试看： (X) Airplanes make to travel around the world in a short time possible. 现行英语不成立。