If f(x)=−x2−8x+7 and g(x)=x−1, what does (g−f)(x) equal?
A)(g−f)(x)=−x2−9x+8
B)(g−f)(x)=−x2−7x+6
C)(g−f)(x)=−8x+8
D)(g−f)(x)=x2+9x−8