I recently answered the following question:
and although I don't think it's written in the clearest possible way, I (and another answerer) had no trouble understanding the question.
The question was nonetheless put on hold (due to the votes of a number of users) for being unclear. I'm pretty confused by this to be honest.
Is what the OP is asking really sufficiently unclear for it to be closed? He pretty clearly states that he just wants to know how the derivative operator was "factored out" of a particular expression. I would be much less confused if, for example, the question had been moved to math.SE instead of being closed as unclear.
Perhaps I'm just clairvoyant and I don't know it? Perhaps I'm just confused about the SE definition of "clarity"? I dunno.