后边加介词to，例如：
1、These words send a strong message. They say that you do not need to be extremely to understand something.这句话传达出很明确的信息，就是说，你不需要很聪明就能理解一些东西。
2、She found it extremely difficult to get a job.她发觉找工作极其困难。
3、It's still extremely difficult to get tenure.要取得终身职位仍然极其困难。