f(x)=x^2-3x+9

g(x)=3x^3+2x^2-4x-9
find (f-g)(x)
a)3x^3-x^2-x
b)-3x^3-x^2+x+18
c)3x^3+x^2-x-18
d)3x^3+3x^2-7x

1 answer

To find \((f - g)(x)\), we need to subtract \(g(x)\) from \(f(x)\).

Given: \[ f(x) = x^2 - 3x + 9 \] \[ g(x) = 3x^3 + 2x^2 - 4x - 9 \]

Now, let's compute \((f - g)(x)\):

\[ (f - g)(x) = f(x) - g(x) \] \[ = (x^2 - 3x + 9) - (3x^3 + 2x^2 - 4x - 9) \]

Distributing the negative sign to \(g(x)\): \[ = x^2 - 3x + 9 - 3x^3 - 2x^2 + 4x + 9 \]

Now, combine like terms:

  • The \(x^3\) term: \(-3x^3\)
  • The \(x^2\) terms: \(x^2 - 2x^2 = -x^2\)
  • The \(x\) terms: \(-3x + 4x = x\)
  • The constant terms: \(9 + 9 = 18\)

Putting it all together: \[ (f - g)(x) = -3x^3 - x^2 + x + 18 \]

Thus, the answer corresponds to option: \[ \boxed{-3x^3 - x^2 + x + 18} \]