Is there a difference between these two forms ?
1- A dog is considered old if it lives seven years.
2- A dog is considered to be old if it lives seven years.
There is no difference in meaning, the choice is a matter of style
This question was discussed on the English Language and Usage Exchange and has some good answers if you're curious to read more on the topic of when/why it is acceptable to drop "to be" in some cases.
