"Agreed" is an expression that means that there is agreement, that all sides involved agree. Being in agreement is when everything is accepted, when the parties reconcile opinions or situations.
The expression "in agreement" is formed by the union of the preposition "of" plus the word "agreement", noun masculine meaning the action of entering into agreement, or what was agreed between two or more parts.
Together, the words form the idea of having an agreement, that is, establishing a common decision, a conclusion whether for an obstacle or discussion. They are all in agreement, that is to say that they are agreed among themselves, with nothing more to discuss about this demand.
For example, when putting a certain subject on the agenda at a meeting, after a period of discussion about the decision, the meeting leader questions everyone present:
"everyone agree?"
And only after they agree that it moves on to the next agenda.
The expression "by mutual agreement" to indicate that the parties have a joint decision.
"Agreed" has how synonyms the words and expressions: accept, agree, assent, agree, agree, consent, agree, understood, okay.
"According to" is an added variation of yet another preposition, "with" and means "in conformity". Widely used in texts to introduce citations or external references. As in the sentence:
"According to Plato, the function of the human soul is to be virtuous."
The expression "according to" has as synonyms the words second, conforming, conforming with, and consonant.
Agree or Agree
The correct spelling is in accordance, separate. A written agreement does not exist in the Portuguese language.