Which function rule represents h(x) as an independent function?

f(x)=6x2−3x−9
g(x)=2x2+4x+8
h(x)=f(x)−g(x)

Answer Choices:

h(x)=4x2−7x−17
h(x)=x+x
h(x)=4x2+x+1
h(x)=x−x
h(x)=4x2−x−1
h(x)=−4x2+7x+17