Is "from" not necessary when I use "blow out"? I thought "blow something out from your ass" is right one.

Native speaker’s answer
Rebecca
Both the prepositions "from" and "of" can be used in this context to say "out from" or "out of". However, the preposition is omitted in this case because the word "out" already gives a direction and implies that it came from "your ass" here. Skipping the preposition here makes the sentence sound more casual and informal. It is not proper grammar, however, it is a common way of speaking.