Grammar notes: the passive
The passive is used when you move the focus of an active sentence from the subject to the object, for example:
The passive is used when you move the focus of an active sentence.
I've used the passive in the first part of the sentence because it's the most important thing, but then I've changed to the active because it's you who has to decide to move the focus of the sentence or not.
I've probably made things too complicated here, so a more typical example would be:
Hamlet was written by Shakespeare.
Shakespeare wrote Hamlet.
In the first example I'm concentrating on the play, Hamlet, and not on the person who wrote it. In the second example I'm more interested in Shakespeare himself.
The passive form is often associated with written and/or more formal language. This is true to a certain extent, but it doesn't mean passive=formal, active=informal.
Using the active form can make writing appear more vivid and alive, while using the passive can hide identity. Both forms therefore have their uses that have little to do with being formal or not.
The passive is very easy to form:
subject + to be in relevant tense + past participle
Just change the verb to be to whatever tense you need. The past participle never changes.
will have been
There are passive infinitives and gerunds which are also formed with the verb to be:
The work should be finished by Friday.
No work needs to be done over the weekend.
Being punished for bad behaviour is normal at school.
Potatoes have to be washed before being cooked.
BY OR WITH?
In the passive voice, we use:
This omelette was made with eggs, potatoes and onions. (eggs, potatoes and onions = the material that was used)
The agent would be the subject of an active sentence. It is introduced using by:
That film was directed by Hitchcock.
The dinner is being cooked by my sister.
The prisoner was shot by the police trying to escape.
You don't need to include the agent if you don't know it, if it doesn't matter, or if it's obvious:
He was arrested yesterday (by the police, obviously).
The building I live in was built in the 1920s (but I don't know who built it, and it doesn't matter anyway).
You aren't allowed to smoke in here (by law / by the management).
This is the part Spanish people don't like at all. However, this form is often used in English, especially in things like newspaper reports.
It + passive reporting verb + that + clause
subject + passive reporting verb + to infinitive
Both these structures are used, but the first one is probably the most usual because it can be used with almost any sentence:
It is said that twenty people have died in the explosion.
Twenty people are said to have died in the explosion.
It is believed that the prime minister is on the point of resigning.
The prime minister is believed to be on the point of resigning.
It was agreed that the strike would end at midnight.
It has been estimated that 200 new jobs will be created.
The equivalent structure in Spanish is often the reflexive:
Se dice que...
Se supone que...
Some of the verbs you can use with this structure are believe, calculate, claim, consider, discover, estimate, feel, hope, know, prove, report, say, show, think, understand, etc.