一道英语分析题I found his speech difficult to understand .此句中为什么用to

1.find有此特殊结构,类似动词还有make/feel/think/consider等.
2.此结构楼主表达有误,应该是：
find + 宾语（名词/代词）+ 形容词 + 不含宾语的不定式（to do）
而且,如果不定式中的动词如果是不及物动词,还必须在其后再加上相应的介词.
该结构对形容词没有特殊的规定,只要可以修饰物体,表示其特性的形容词即可.
3.该结构可以做如下变化：
find + n./pron.+ adj.+ to do
= find it + adj.+ to do + n./pron.
= find (that) it + be + adj.+ to do + n./pron.
如：I found his speech difficult to understand.
= I found it difficult to understand his speech.
= I found (that) it was difficult to understand his speech.
再如：I find him hard to get along with.
= I find it hard to get along with him.
= I find (that) it is hard to get along with him.

difficult to do sth. 做某事困难
find的过去式是found
对形容词没什么特殊的要求，但不能乱用吧

difficult to do sth. 做某事困难，就像easy to do sth.
对于这个句子，形容词应该是像difficult，easy，hard这类词，具体也说不清楚。这类词经常出现在这种句型中
另外你觉得什么形容词不合适，necessary，important，形容词应该都行。

found 是动词，understand 也是动词，2个动词连用就要用to 隔开，也就是说动词＋to ＋动词，至于adj ，adj 是形容词，形容词不能变，只要是形容词就可以了。懂了没啊。