request vs ask; right usage;

Question

What word "request" or "ask" is more appropriate if we are talking about formal letter?

1. I am writing to request few days off.
   
   
2. I am writing to ask about few days off.

Thanks.

Answer 1

"Request <something>" = "Ask for <something>", so you could write

I am writing to request a few days off.

or

I am writing to ask for a few days off.

The phrase "to ask about" is less appropriate here unless you are looking for an explanation or clarification.

Answer 2

You don't really say why you are asking. If you are making a formal request for time off, then:

I am writing to request a few days off.

But if you are asking if taking time off is possible, then:

I am writing to ask about the possibility of taking a few days off.

or

I am writing to ask about taking a few days off.