To find the profit function \( P(x) \), we need to subtract the expenses \( g(x) \) from the revenue \( f(x) \).
The functions given are:
- Revenue function: \( f(x) = 2x^4 + x^3 - 4x + 20 \)
- Expense function: \( g(x) = -x^3 + x^2 + 50 \)
The profit function \( P(x) \) is given by:
\[ P(x) = f(x) - g(x) \]
Substituting in the values for \( f(x) \) and \( g(x) \):
\[ P(x) = (2x^4 + x^3 - 4x + 20) - (-x^3 + x^2 + 50) \]
Distributing the negative sign:
\[ P(x) = 2x^4 + x^3 - 4x + 20 + x^3 - x^2 - 50 \]
Combining like terms:
\[ P(x) = 2x^4 + (x^3 + x^3) - x^2 - 4x + (20 - 50) \] \[ P(x) = 2x^4 + 2x^3 - x^2 - 4x - 30 \]
Thus, the profit function is:
\[ P(x) = 2x^4 + 2x^3 - x^2 - 4x - 30 \]
Now, regarding the domain, since \( x \) represents years after starting the company, \( x \) must be non-negative. Therefore, the domain is:
\[ \text{Domain: } x \geq 0 \]
In conclusion, the correct response is:
\[ \boxed{(f-g)(x) = 2x^4 + 2x^3 - x^2 - 4x - 30 \text{ and the domain is } x \geq 0.} \]