Answer:
x²+5x
Explanation:
You can make (f-g)(x) into (x) - (-x²-4x) because f(x)=x and g(x)=x²-4x
(x)-(-x²-4x) can simplify into x+x²+4x once you distribute the negative sign.
x+x²+4x simplifies into x²+5x.
So your final answer is x²+5x.
I hope it's right and this helps!