Answer
$f(x)-g(x) = -5x^3-5x^2+14x+12$, or (A)
Work Step by Step
For this, subtract "like terms", or terms with the same power of x, of g(x) from f(x) and put the results together.
$x^3$ terms: $x^3 - 6x^3 = -5x^3$
$x^2$ terms: $-4x^2-x^2 = -5x^2$
$x$ terms: $9x-(-5x) = 9x+5x=14x$
Number terms: $0-(-12) = 12$
$f(x)-g(x) = -5x^3-5x^2+14x+12$, or (A)
