Substitute -2x for f(x) in -f(x) and simplify.

Answer 1

To substitute -2x for f(x) in -f(x), we have to replace every occurrence of f(x) with -2x.

Therefore, -f(x) becomes -(-2x).

Simplifying, --2x becomes 2x.

So, substituting -2x for f(x) in -f(x), we get 2x.