Thanks for the reply!
It was not covered in class for any clarification. It was perfectly acceptable to have "-1 * x" or similar and my solution was correctly simplified. I was told that a double negative was simply not valid for working.
The reason I was asking about the question was to not...
An assignment of mine was returned with point deductions for writing:
"-1.x- - y.x" and was told it must be written "-1.x -(-y).x"
I asked about it and was told you can't have double negatives in working. I lost approximately 20% worth of the question, despite having perfect working for two...