Answer
$(f-g)(x)=-4x^3-x^2+4x+8$.
$(f-g)(-1)=7$.
Work Step by Step
The given functions are
$f(x)=-3x^3-2x^2-x+4$
$g(x)=x^3-x^2-5x-4$
$(f-g)(x)=f(x)-g(x)$
Plug the given functions
$(f-g)(x)=(-3x^3-2x^2-x+4)-(x^3-x^2-5x-4)$
Clear the parentheses.
$(f-g)(x)=-3x^3-2x^2-x+4-x^3+x^2+5x+4$
Add like terms.
$(f-g)(x)=-4x^3-x^2+4x+8$
Plug $x=-1$
$(f-g)(-1)=-4(-1)^3-(-1)^2+4(-1)+8$
Clear the parentheses.
$(f-g)(-1)=+4-1-4+8$
Simplify.
$(f-g)(-1)=7$.
