Negative sign in front of a number

Question

Does $-a$ mean $(-1)a$ for a real number $a$?

Answer 1

Yes. -a means both (-1)a and 0 - a, which are usually the same thing.

Note if a is negative -a is positive. Ex. -(-7) = 7. And 0 -(-7) = 7.

You should try to mark this take for the appropriate subject though.

Answer 2

Just a small clarification: "$-$" is the abbreviation of "$-1\cdot{}$", hence $-a=-1\cdot a$. Parentheses are not necessary.