De virker utslitte.

Only because it is the first word in the sentence. In the middle of a sentence, it would normally be written de.

Here it is the ordinary pronoun they, not the old-fashioned polite De meaning you.

Here it means they.

You can tell because de is being used as the subject of the verb virker. If de means those, it usually appears with a noun, for example de bøkene = those books.

Here virker means seem or appear.

It is the present tense of å virke. This verb can also mean work/function in other contexts, such as Maskinen virker = The machine works. In this sentence, because it is followed by an adjective, it clearly means seem.

Because Norwegian verbs do not change form for person or number in the present tense.

So you get:

• jeg virker
• du virker
• han/hun virker
• vi virker
• de virker

This is simpler than English, where you have I seem but he seems.

Because utslitte agrees with the plural subject de.

Utslitt is the adjective in the singular form, while utslitte is the plural form. Since de is plural, the adjective must also be plural:

• Han virker utslitt = one person
• De virker utslitte = more than one person

Yes.

The difference is:

• De er utslitte = they are exhausted
• De virker utslitte = they seem exhausted

So virker makes the statement a little less direct. It shows that this is your impression, not necessarily a confirmed fact.

Both can describe being tired, but utslitt is usually stronger.

• sliten = tired, worn out
• utslitt = exhausted, completely worn out

Sliten is very common in everyday speech for ordinary tiredness. Utslitt often suggests a deeper level of exhaustion.

Because utslitte is a predicate adjective here. After verbs like være, bli, and virke, Norwegian normally uses the adjective directly, without an article.

So:

• De virker utslitte = correct

But when the adjective comes before a noun, it is part of a noun phrase:

• de utslitte arbeiderne = the exhausted workers

Not exactly.

• virke = seem, come across as
• se ut = look

So De virker utslitte is about the overall impression.
If you want to focus more on visual appearance, you could say:

De ser utslitte ut.

That is also a very natural sentence in Norwegian.

Yes.

For people, it means exhausted or worn out.
For things, it means worn out from use.

For example:

• Jeg er utslitt = I am exhausted
• Skoene er utslitte = The shoes are worn out

So the exact nuance depends on what is being described.