How to use this word?

Question

"considered"

considered to

considered by

i don't understand the difference

Answer 1

I was considered to be extremely shy by my classmates.

I can tell my report was considered by the questions I was asked following the meeting.

Answer 2

The thing was considered to be big.

The thing was considered by a person to be big.

Answer 3

For a consideration I will consider your question.

The first would be used in sentences like.  

He is considered to be an ax murderer.

The latter would be used in a sentence as..

But He is considered by his mother to be just a little edgy.  

Answer 4

I have considered to go to university after finishing college.

It was considered unladylike by men in the Victorian era for women to go to university.